diff --git a/apps/admin-web/src/components/OssUpload.tsx b/apps/admin-web/src/components/OssUpload.tsx
index 12f1634..314edf2 100644
--- a/apps/admin-web/src/components/OssUpload.tsx
+++ b/apps/admin-web/src/components/OssUpload.tsx
@@ -1,5 +1,5 @@
-import { useState } from 'react';
-import { Button, Image, Input, Modal, Space, Upload, message } from 'antd';
+import { useState, type ReactNode } from 'react';
+import { Button, Image, Input, Modal, Space, Typography, Upload, message } from 'antd';
 import { EyeOutlined, FilePdfOutlined, UploadOutlined } from '@ant-design/icons';
 import type { UploadProps } from 'antd';
 import { uploadFileToOss, type OssMediaType, type UploadFileResult } from '../lib/upload';
@@ -13,6 +13,7 @@ type OssUploadProps = {
   accept?: string;
   maxSizeMb?: number;
   placeholder?: string;
+  uploadHint?: ReactNode;
 };
 
 function isImageUrl(url: string) {
@@ -23,6 +24,32 @@ function isPdfUrl(url: string) {
   return /\.pdf(\?|#|$)/i.test(url);
 }
 
+function formatUploadImageMessage(result: UploadFileResult): string {
+  const img = result.image;
+  if (!img) return '上传成功';
+  const sizeLabel = `${img.width}×${img.height}`;
+  if (img.compressed && img.originalWidth && img.originalHeight) {
+    const original = `${img.originalWidth}×${img.originalHeight}`;
+    if (original !== sizeLabel) {
+      return `上传成功（${sizeLabel}，已由 ${original} 自动压缩）`;
+    }
+  }
+  return `上传成功（${sizeLabel}）`;
+}
+
+function formatUploadImageHint(result: UploadFileResult): string | null {
+  const img = result.image;
+  if (!img) return null;
+  const sizeLabel = `${img.width}×${img.height}`;
+  if (img.compressed && img.originalWidth && img.originalHeight) {
+    const original = `${img.originalWidth}×${img.originalHeight}`;
+    if (original !== sizeLabel) {
+      return `${sizeLabel}（已由 ${original} 自动压缩）`;
+    }
+  }
+  return sizeLabel;
+}
+
 export default function OssUpload({
   value,
   onChange,
@@ -31,9 +58,11 @@ export default function OssUpload({
   mediaType = 'IMAGE',
   accept,
   placeholder = '上传后自动填入，或手动粘贴 URL',
+  uploadHint,
 }: OssUploadProps) {
   const [uploading, setUploading] = useState(false);
   const [pdfPreviewOpen, setPdfPreviewOpen] = useState(false);
+  const [imageMetaHint, setImageMetaHint] = useState<string | null>(null);
 
   const resolvedAccept =
     accept ?? (mediaType === 'VIDEO' ? 'video/*' : mediaType === 'FILE' ? undefined : 'image/*');
@@ -45,7 +74,9 @@ export default function OssUpload({
       const result = await uploadFileToOss(raw, { bizType, mediaType });
       onChange?.(result.url);
       onUploaded?.(result);
-      message.success('上传成功');
+      const successMessage = formatUploadImageMessage(result);
+      setImageMetaHint(formatUploadImageHint(result));
+      message.success(successMessage);
       onSuccess?.(result);
     } catch (e) {
       const err = e instanceof Error ? e : new Error('上传失败');
@@ -116,6 +147,16 @@ export default function OssUpload({
         <video src={value} controls style={{ maxWidth: '100%', maxHeight: 160, borderRadius: 4 }} />
       )}
       {filePreview}
+      {uploadHint ? (
+        <Typography.Text type="secondary" style={{ fontSize: 12 }}>
+          {uploadHint}
+        </Typography.Text>
+      ) : null}
+      {imageMetaHint ? (
+        <Typography.Text type="secondary" style={{ fontSize: 12 }}>
+          当前底图：{imageMetaHint}
+        </Typography.Text>
+      ) : null}
       <Space wrap>
         <Upload
           accept={resolvedAccept}
diff --git a/apps/admin-web/src/lib/upload.ts b/apps/admin-web/src/lib/upload.ts
index 106e019..1cdeece 100644
--- a/apps/admin-web/src/lib/upload.ts
+++ b/apps/admin-web/src/lib/upload.ts
@@ -4,6 +4,7 @@ import {
   DEFAULT_OSS_MAX_UPLOAD_BYTES,
   formatOssMaxSizeMb,
 } from '@dukang/shared-ui/compressImage';
+import type { OssUploadImageMeta } from '@dukang/shared-types';
 
 export type OssMediaType = 'IMAGE' | 'VIDEO' | 'FILE';
 
@@ -12,6 +13,7 @@ export type UploadFileResult = {
   ossKey: string;
   bucket: string;
   mock: boolean;
+  image?: OssUploadImageMeta;
 };
 
 async function prepareUploadFile(file: File, mediaType: OssMediaType): Promise<File> {
diff --git a/apps/admin-web/src/pages/ActivityPostersPage.tsx b/apps/admin-web/src/pages/ActivityPostersPage.tsx
index ad55a65..874c63f 100644
--- a/apps/admin-web/src/pages/ActivityPostersPage.tsx
+++ b/apps/admin-web/src/pages/ActivityPostersPage.tsx
@@ -6,6 +6,7 @@ import {
 import type { ColumnsType } from 'antd/es/table';
 import {
   ACTIVITY_POSTER_STATUS_LABELS,
+  ACTIVITY_POSTER_UPLOAD_HINT,
   DEFAULT_ACTIVITY_POSTER_QR_SLOT,
   type ActivityPosterItem,
   type ActivityPosterQrSlot,
@@ -280,7 +281,7 @@ export default function ActivityPostersPage() {
             <Input maxLength={128} />
           </Form.Item>
           <Form.Item name="imageUrl" label="活动图" rules={[{ required: true, message: '请上传活动图' }]}>
-            <OssUpload bizType="ACTIVITY_POSTER" />
+            <OssUpload bizType="ACTIVITY_POSTER" uploadHint={ACTIVITY_POSTER_UPLOAD_HINT} />
           </Form.Item>
           <Form.Item name="qrXPct" hidden><InputNumber /></Form.Item>
           <Form.Item name="qrYPct" hidden><InputNumber /></Form.Item>
diff --git a/docs/杜康好客-v4-现状对照.md b/docs/杜康好客-v4-现状对照.md
index 67a736a..4d36ff3 100644
--- a/docs/杜康好客-v4-现状对照.md
+++ b/docs/杜康好客-v4-现状对照.md
@@ -10,7 +10,7 @@
 | 版本线 | **v4.0.15** HQ 概览折线图（粒度分桶、总量/增量、维度线条） |
 | 订单佣金 | 区县归属已删除；只认关联 / 代下单选择 |
 | 账单 | 酒订单 / 核销订单分列；合伙人改为周账（周一 08:00）；零元不同步合伙人；酒厂含现场提货，零应付仍出账（无需打款） |
-| 活动图 | HQ 上传底图/码栏/文案；合伙人选择写入库；HQ 可指定一张图为勾选主合伙人合成下载；子账号不可看活动图 |
+| 活动图 | HQ 上传底图/码栏/文案；**v4.0.15 上传超限自动压缩并提示尺寸**；合伙人选择写入库；HQ 可指定一张图为勾选主合伙人合成下载；子账号不可看活动图 |
 
 ## 1. 版本交付
 
@@ -36,4 +36,4 @@
 | 2026-09-02 | v4.0.9：子账号默认启用；关联码已扫码；零元账单不同步；银行账号自填；周账周一 08:00；预付款预估；子账号用户管理无活动图 |
 | 2026-09-02 | v4.0.13：收货禁「全市」；脏地址下单拦截；小飞侠超区/推单失败挂 `fulfillmentHold`（不做仓/收件坐标） |
 | 2026-09-02 | v4.0.14：HQ 概览日/周/月/季/年、环比；全局城市/时间 + 五板块筛；订单/核销笔数与金额 |
-| 2026-09-02 | v4.0.15：HQ 概览改为全宽折线图；去掉板块筛；查看快链只带全局城市与日期 |
+| 2026-09-02 | v4.0.15：HQ 概览改为全宽折线图；去掉板块筛；查看快链只带全局城市与日期；活动图上传超限自动压缩并提示尺寸 |
diff --git a/docs/杜康好客-v4.0.15-开发文档.md b/docs/杜康好客-v4.0.15-开发文档.md
index ef2a4b7..ed94b66 100644
--- a/docs/杜康好客-v4.0.15-开发文档.md
+++ b/docs/杜康好客-v4.0.15-开发文档.md
@@ -77,3 +77,38 @@
 - [ ] 客服无合伙人/门店/核销图
 - [ ] 待办卡与超管发版区不变
 - [ ] domain 折线单测通过
+
+---
+
+## 6. 活动图上传压缩（DPT-20260902-849）
+
+### 6.1 目标
+
+HQ 上传活动底图时，后端用 Sharp 自动等比缩放至 v4.0.7 底图限制（最长边 ≤ 2500px、宽×高 ≤ 400 万），并在响应与表单中提示尺寸。
+
+### 6.2 规则
+
+- 入口：`POST /common/resources/upload`，`bizType=ACTIVITY_POSTER`、`mediaType=IMAGE`
+- 尺寸合规：原样存 OSS，响应 `image.compressed=false`
+- 尺寸超限：Sharp 等比缩放后存 OSS，响应含 `width/height/originalWidth/originalHeight/compressed`
+- 有 alpha 通道保留 PNG；否则按原 mime 或 JPEG quality 85 输出
+- 压缩后仍超过 `OSS_MAX_UPLOAD_BYTES` → 4xx，文案含当前尺寸
+- **手动粘贴 URL** 仍不经上传压缩；合成时沿用 v4.0.7 校验
+
+### 6.3 变更面
+
+| 层 | 路径 |
+|----|------|
+| shared-types | `activity-poster.ts`：`activityPosterResizeTarget`、`OssUploadImageMeta`、`ACTIVITY_POSTER_UPLOAD_HINT` |
+| API | `common/image/activity-poster-upload.util.ts`、`resource.service.ts` |
+| HQ | `OssUpload.tsx`、`ActivityPostersPage.tsx`、`lib/upload.ts` |
+
+无 Prisma 迁移。
+
+### 6.4 验收
+
+- [ ] 上传 1080×1920：成功，提示尺寸，未标记压缩
+- [ ] 上传 4000×3000：成功，提示压缩后尺寸与原尺寸
+- [ ] 保存后「为该合伙人下载」/ zip 导出不再报底图过大
+- [ ] 非图片 / 损坏文件：明确 4xx
+- [ ] AVATAR 等其他 bizType 行为不变
diff --git a/packages/shared-types/src/activity-poster.test.ts b/packages/shared-types/src/activity-poster.test.ts
index ea23593..2f3e176 100644
--- a/packages/shared-types/src/activity-poster.test.ts
+++ b/packages/shared-types/src/activity-poster.test.ts
@@ -2,6 +2,7 @@ import { describe, expect, it } from 'vitest';
 import {
   activityPosterPackFileName,
   activityPosterQrSlotPx,
+  activityPosterResizeTarget,
   activityPosterTemplateTooLarge,
 } from './activity-poster';
 
@@ -37,6 +38,30 @@ describe('activityPosterTemplateTooLarge', () => {
   });
 });
 
+describe('activityPosterResizeTarget', () => {
+  it('returns null for 1080x1920', () => {
+    expect(activityPosterResizeTarget(1080, 1920)).toBeNull();
+  });
+
+  it('scales edge over 2500', () => {
+    const target = activityPosterResizeTarget(4000, 3000);
+    expect(target).not.toBeNull();
+    expect(Math.max(target!.width, target!.height)).toBeLessThanOrEqual(2500);
+    expect(activityPosterTemplateTooLarge(target!.width, target!.height)).toBe(false);
+  });
+
+  it('scales pixel count over 4e6', () => {
+    const target = activityPosterResizeTarget(2500, 2000);
+    expect(target).not.toBeNull();
+    expect(target!.width * target!.height).toBeLessThanOrEqual(4_000_000);
+    expect(activityPosterTemplateTooLarge(target!.width, target!.height)).toBe(false);
+  });
+
+  it('does not upscale small images', () => {
+    expect(activityPosterResizeTarget(100, 100)).toBeNull();
+  });
+});
+
 describe('activityPosterPackFileName', () => {
   it('uses city, company, id', () => {
     expect(activityPosterPackFileName({
diff --git a/packages/shared-types/src/activity-poster.ts b/packages/shared-types/src/activity-poster.ts
index 2d86e76..b5786be 100644
--- a/packages/shared-types/src/activity-poster.ts
+++ b/packages/shared-types/src/activity-poster.ts
@@ -72,6 +72,39 @@ export function activityPosterTemplateTooLarge(width: number, height: number): b
   return w > ACTIVITY_POSTER_MAX_EDGE || h > ACTIVITY_POSTER_MAX_EDGE || w * h > ACTIVITY_POSTER_MAX_PIXELS;
 }
 
+/** HQ 上传活动图时的尺寸说明（前后端共用文案） */
+export const ACTIVITY_POSTER_UPLOAD_HINT =
+  '底图最长边不超过 2500px，总像素不超过 400 万；超出将自动压缩';
+
+export type OssUploadImageMeta = {
+  width: number;
+  height: number;
+  originalWidth?: number;
+  originalHeight?: number;
+  compressed: boolean;
+  fileSize: number;
+};
+
+/** 若底图超限，返回等比缩放后的目标宽高；否则 null（不放大） */
+export function activityPosterResizeTarget(
+  width: number,
+  height: number,
+): { width: number; height: number } | null {
+  const w = Math.max(1, Math.round(width));
+  const h = Math.max(1, Math.round(height));
+  if (!activityPosterTemplateTooLarge(w, h)) return null;
+
+  const maxEdge = Math.max(w, h);
+  const scaleEdge = maxEdge > ACTIVITY_POSTER_MAX_EDGE ? ACTIVITY_POSTER_MAX_EDGE / maxEdge : 1;
+  const scalePixels = w * h > ACTIVITY_POSTER_MAX_PIXELS ? Math.sqrt(ACTIVITY_POSTER_MAX_PIXELS / (w * h)) : 1;
+  const scale = Math.min(scaleEdge, scalePixels);
+
+  return {
+    width: Math.max(1, Math.round(w * scale)),
+    height: Math.max(1, Math.round(h * scale)),
+  };
+}
+
 /** zip / 单张下载文件名：`{城市}_{公司或姓名}_{id}.png` */
 export function activityPosterPackFileName(input: {
   cityName?: string | null;
diff --git a/server/dukang-api/src/common/image/activity-poster-upload.util.ts b/server/dukang-api/src/common/image/activity-poster-upload.util.ts
new file mode 100644
index 0000000..c91b61a
--- /dev/null
+++ b/server/dukang-api/src/common/image/activity-poster-upload.util.ts
@@ -0,0 +1,101 @@
+import { BadRequestException } from '@nestjs/common';
+import {
+  activityPosterResizeTarget,
+  activityPosterTemplateTooLarge,
+} from '@dukang/shared-types';
+import sharp from 'sharp';
+
+const JPEG_QUALITY = 85;
+
+export type ActivityPosterUploadPrepared = {
+  buffer: Buffer;
+  mimeType: string;
+  width: number;
+  height: number;
+  originalWidth: number;
+  originalHeight: number;
+  compressed: boolean;
+};
+
+function resolveOutputMime(hasAlpha: boolean, inputMime?: string): string {
+  if (hasAlpha) return 'image/png';
+  if (inputMime === 'image/webp') return 'image/jpeg';
+  if (inputMime?.startsWith('image/')) return inputMime;
+  return 'image/jpeg';
+}
+
+async function encodeImage(
+  pipeline: sharp.Sharp,
+  mimeType: string,
+): Promise<Buffer> {
+  if (mimeType === 'image/png') {
+    return pipeline.png().toBuffer();
+  }
+  if (mimeType === 'image/jpeg' || mimeType === 'image/jpg') {
+    return pipeline.jpeg({ quality: JPEG_QUALITY }).toBuffer();
+  }
+  if (mimeType === 'image/webp') {
+    return pipeline.webp({ quality: JPEG_QUALITY }).toBuffer();
+  }
+  return pipeline.jpeg({ quality: JPEG_QUALITY }).toBuffer();
+}
+
+export async function prepareActivityPosterUpload(input: {
+  buffer: Buffer;
+  mimeType?: string;
+}): Promise<ActivityPosterUploadPrepared> {
+  if (!input.buffer?.length) {
+    throw new BadRequestException('活动图文件为空');
+  }
+  if (input.mimeType && !input.mimeType.startsWith('image/')) {
+    throw new BadRequestException('活动图仅支持图片文件');
+  }
+
+  const meta = await sharp(input.buffer, { failOn: 'none' }).metadata();
+  if (!meta.width || !meta.height) {
+    throw new BadRequestException('活动图无法读取尺寸，请换一张图片');
+  }
+
+  const originalWidth = meta.width;
+  const originalHeight = meta.height;
+  const resizeTarget = activityPosterResizeTarget(originalWidth, originalHeight);
+
+  if (!resizeTarget) {
+    return {
+      buffer: input.buffer,
+      mimeType: input.mimeType || 'image/jpeg',
+      width: originalWidth,
+      height: originalHeight,
+      originalWidth,
+      originalHeight,
+      compressed: false,
+    };
+  }
+
+  const hasAlpha = meta.hasAlpha === true;
+  const outputMime = resolveOutputMime(hasAlpha, input.mimeType);
+  const buffer = await encodeImage(
+    sharp(input.buffer, { failOn: 'none' }).resize(resizeTarget.width, resizeTarget.height, {
+      fit: 'inside',
+      withoutEnlargement: true,
+    }),
+    outputMime,
+  );
+  const metaOut = await sharp(buffer).metadata();
+  const width = metaOut.width ?? resizeTarget.width;
+  const height = metaOut.height ?? resizeTarget.height;
+
+  if (activityPosterTemplateTooLarge(width, height)) {
+    throw new BadRequestException('活动图压缩后仍超出尺寸限制，请换一张较小的图片');
+  }
+
+  return {
+    buffer,
+    mimeType: outputMime,
+    width,
+    height,
+    originalWidth,
+    originalHeight,
+    compressed: true,
+  };
+}
diff --git a/server/dukang-api/src/modules/common/resource.service.ts b/server/dukang-api/src/modules/common/resource.service.ts
index 23d01cb..1aa86af 100644
--- a/server/dukang-api/src/modules/common/resource.service.ts
+++ b/server/dukang-api/src/modules/common/resource.service.ts
@@ -3,6 +3,7 @@ import type { ResourceBizType, ResourceMediaType, ResourceOwnerType } from '@pri
 import { Prisma } from '@prisma/client';
 import { PrismaService } from '../../common/prisma/prisma.module';
 import { serializeBigInt } from '../../common/decorators/current-user.decorator';
+import { prepareActivityPosterUpload } from '../../common/image/activity-poster-upload.util';
 import { OSS_PROVIDER } from '../../integrations/integrations.constants';
 import type { IOssProvider } from '../../integrations/oss/oss.interface';
 import { logOssUpload, type OssActorRef } from '../../integrations/oss/oss-log.util';
@@ -105,19 +106,75 @@ export class ResourceService {
     if (dto.bizType === 'AVATAR' && !file.mimetype?.startsWith('image/')) {
       throw new BadRequestException('头像仅支持图片文件');
     }
+    if (dto.bizType === 'ACTIVITY_POSTER' && dto.mediaType === 'IMAGE' && !file.mimetype?.startsWith('image/')) {
+      throw new BadRequestException('活动图仅支持图片文件');
+    }
+
+    let uploadBuffer = file.buffer;
+    let uploadMimeType = file.mimetype;
+    let imageMeta: {
+      width: number;
+      height: number;
+      originalWidth: number;
+      originalHeight: number;
+      compressed: boolean;
+      fileSize: number;
+    } | undefined;
+
+    if (dto.bizType === 'ACTIVITY_POSTER' && dto.mediaType === 'IMAGE') {
+      const prepared = await prepareActivityPosterUpload({
+        buffer: file.buffer,
+        mimeType: file.mimetype,
+      });
+      if (prepared.buffer.length > maxUploadBytes) {
+        const message = `活动图压缩后仍超过 ${Math.floor(maxUploadBytes / 1024 / 1024)}MB（当前 ${prepared.width}×${prepared.height}）`;
+        await logOssUpload(this.prisma, {
+          scene: 'UPLOAD_PUT_OBJECT',
+          actorRef: actor,
+          requestBody: {
+            ...requestBody,
+            imageWidth: prepared.width,
+            imageHeight: prepared.height,
+            compressed: prepared.compressed,
+          },
+          status: 'FAILED',
+          errorMessage: message,
+        });
+        throw new BadRequestException(message);
+      }
+      uploadBuffer = prepared.buffer;
+      uploadMimeType = prepared.mimeType;
+      imageMeta = {
+        width: prepared.width,
+        height: prepared.height,
+        originalWidth: prepared.originalWidth,
+        originalHeight: prepared.originalHeight,
+        compressed: prepared.compressed,
+        fileSize: prepared.buffer.length,
+      };
+    }
 
     try {
       const result = await this.oss.putObject({
         bizType: dto.bizType,
         mediaType: dto.mediaType,
         fileName: file.originalname || 'upload.bin',
-        buffer: file.buffer,
-        mimeType: file.mimetype,
+        buffer: uploadBuffer,
+        mimeType: uploadMimeType,
       });
       await logOssUpload(this.prisma, {
         scene: 'UPLOAD_PUT_OBJECT',
         actorRef: actor,
-        requestBody,
+        requestBody: {
+          ...requestBody,
+          ...(imageMeta
+            ? {
+                imageWidth: imageMeta.width,
+                imageHeight: imageMeta.height,
+                compressed: imageMeta.compressed,
+              }
+            : {}),
+        },
         responseBody: {
           bucket: result.bucket,
           region: result.region,
@@ -139,14 +196,14 @@ export class ResourceService {
             ossKey: result.ossKey,
             url: result.url,
             fileName: file.originalname || 'avatar',
-            fileSize: BigInt(file.size),
-            mimeType: file.mimetype,
+            fileSize: BigInt(uploadBuffer.length),
+            mimeType: uploadMimeType,
             status: 'ACTIVE',
           },
         });
-        return serializeBigInt({ ...result, resourceId: resource.id });
+        return serializeBigInt({ ...result, resourceId: resource.id, ...(imageMeta ? { image: imageMeta } : {}) });
       }
-      return result;
+      return { ...result, ...(imageMeta ? { image: imageMeta } : {}) };
     } catch (err) {
       await logOssUpload(this.prisma, {
         scene: 'UPLOAD_PUT_OBJECT',