diff --git a/frontend/components/SidebarRail.vue b/frontend/components/SidebarRail.vue
index 116b759..de156fc 100644
--- a/frontend/components/SidebarRail.vue
+++ b/frontend/components/SidebarRail.vue
@@ -195,6 +195,33 @@
         </div>
       </div>
 
+      <!-- ImgHelper (Auto download large images) -->
+      <div
+        class="sidebar-rail-action w-full h-[var(--sidebar-rail-step)] flex items-center justify-center group"
+        :class="imgHelperBusy ? 'opacity-60 cursor-not-allowed' : 'cursor-pointer'"
+        :title="imgHelperTitle"
+        @click="toggleImgHelper"
+      >
+        <div class="sidebar-rail-plate w-[var(--sidebar-rail-btn)] h-[var(--sidebar-rail-btn)] rounded-md flex items-center justify-center transition-colors bg-transparent">
+          <svg
+            class="sidebar-rail-icon w-[var(--sidebar-rail-icon)] h-[var(--sidebar-rail-icon)]"
+            :class="{ 'sidebar-rail-icon-active': imgHelperEnabled }"
+            viewBox="0 0 24 24"
+            fill="none"
+            stroke="currentColor"
+            stroke-width="1.8"
+            stroke-linecap="round"
+            stroke-linejoin="round"
+            aria-hidden="true"
+          >
+            <rect x="3" y="3" width="18" height="18" rx="2" ry="2" />
+            <circle cx="8.5" cy="8.5" r="1.5" />
+            <polyline points="21 15 16 10 5 21" />
+            <path d="M12 9v5m-2-2l2 2 2-2" />
+          </svg>
+        </div>
+      </div>
+
       <!-- Privacy -->
       <div
         class="sidebar-rail-action w-full h-[var(--sidebar-rail-step)] flex items-center justify-center cursor-pointer group"
@@ -368,6 +395,7 @@
 import { storeToRefs } from 'pinia'
 import { useChatAccountsStore } from '~/stores/chatAccounts'
 import { useChatRealtimeStore } from '~/stores/chatRealtime'
+import { useImgHelperStore } from '~/stores/imgHelper'
 import { usePrivacyStore } from '~/stores/privacy'
 import { useThemeStore } from '~/stores/theme'
 
@@ -384,6 +412,10 @@ themeStore.init()
 
 const realtimeStore = useChatRealtimeStore()
 const { enabled: realtimeEnabled, available: realtimeAvailable, checking: realtimeChecking, statusError: realtimeStatusError, toggling: realtimeToggling } = storeToRefs(realtimeStore)
+
+const imgHelperStore = useImgHelperStore()
+const { enabled: imgHelperEnabled, checking: imgHelperChecking, toggling: imgHelperToggling, error: imgHelperError } = storeToRefs(imgHelperStore)
+
 const { open: settingsDialogOpen, openDialog: openSettingsDialog } = useSettingsDialog()
 const { getChatAccountInfo, deleteChatAccount } = useApi()
 
@@ -620,6 +652,18 @@ const toggleRealtime = async () => {
   if (realtimeBusy.value) return
   await realtimeStore.toggle({ silent: false })
 }
+
+const imgHelperBusy = computed(() => !!imgHelperChecking.value || !!imgHelperToggling.value)
+
+const imgHelperTitle = computed(() => {
+  if (imgHelperEnabled.value) return '关闭自动下载大图'
+  return imgHelperError.value || '开启自动下载大图'
+})
+
+const toggleImgHelper = async () => {
+  if (imgHelperBusy.value) return
+  await imgHelperStore.toggle()
+}
 </script>
 
 <style scoped>
diff --git a/frontend/composables/useApi.js b/frontend/composables/useApi.js
index 07fae1f..754f84b 100644
--- a/frontend/composables/useApi.js
+++ b/frontend/composables/useApi.js
@@ -636,8 +636,21 @@ export const useApi = () => {
     return await request(url)
   }
 
+  const getImgHelperStatus = async () => {
+    return await request('/system/img_helper/status')
+  }
+
+  const toggleImgHelper = async (enabled) => {
+    return await request('/system/img_helper/toggle', {
+      method: 'POST',
+      body: { enabled: !!enabled }
+    })
+  }
+
   return {
     pickSystemDirectory,
+    getImgHelperStatus,
+    toggleImgHelper,
     detectWechat,
     detectCurrentAccount,
     decryptDatabase,
diff --git a/frontend/stores/imgHelper.js b/frontend/stores/imgHelper.js
new file mode 100644
index 0000000..a9e7be1
--- /dev/null
+++ b/frontend/stores/imgHelper.js
@@ -0,0 +1,71 @@
+import { defineStore } from 'pinia'
+
+export const useImgHelperStore = defineStore('imgHelper', () => {
+  const enabled = ref(false)
+  const checking = ref(false)
+  const toggling = ref(false)
+  const error = ref('')
+
+  const fetchStatus = async () => {
+    if (!process.client) return
+    const api = useApi()
+    checking.value = true
+    error.value = ''
+    try {
+      const resp = await api.getImgHelperStatus()
+      enabled.value = !!resp?.enabled
+    } catch (e) {
+      error.value = e?.message || '获取插件状态失败'
+    } finally {
+      checking.value = false
+    }
+  }
+
+  const toggle = async () => {
+    if (toggling.value) return
+    
+    const targetState = !enabled.value
+    
+    if (targetState) {
+        // Show warning for first time or every time? User said "首次开启提示hook可能存在风控风险"
+        // We can use localStorage to track if it's the first time.
+        const hasWarned = localStorage.getItem('img_helper_warned')
+        if (!hasWarned) {
+            const confirmed = window.confirm('【安全提示】\n开启“自动下载大图”功能将使用 Hook 技术修改微信内存逻辑。这可能存在一定的风控风险，建议仅在需要时开启。\n\n确认开启吗？')
+            if (!confirmed) return
+            localStorage.setItem('img_helper_warned', 'true')
+        }
+    }
+
+    toggling.value = true
+    error.value = ''
+    const api = useApi()
+    try {
+      const resp = await api.toggleImgHelper(targetState)
+      enabled.value = !!resp?.enabled
+      return true
+    } catch (e) {
+      error.value = e?.message || '操作失败'
+      if (process.client) {
+          window.alert(error.value)
+      }
+      return false
+    } finally {
+      toggling.value = false
+    }
+  }
+
+  // Initialize status
+  if (process.client) {
+    fetchStatus()
+  }
+
+  return {
+    enabled,
+    checking,
+    toggling,
+    error,
+    fetchStatus,
+    toggle
+  }
+})
diff --git a/src/wechat_decrypt_tool/api.py b/src/wechat_decrypt_tool/api.py
index b52fbc9..35f8c88 100644
--- a/src/wechat_decrypt_tool/api.py
+++ b/src/wechat_decrypt_tool/api.py
@@ -37,6 +37,7 @@ from .routers.wechat_detection import router as _wechat_detection_router
 from .routers.wrapped import router as _wrapped_router
 from .request_logging import log_server_errors_middleware
 from .wcdb_realtime import WCDB_REALTIME, shutdown as _wcdb_shutdown
+from .img_helper import IMG_HELPER
 from .routers.biz import router as _biz_router
 from .routers.system import router as _system_router
 
@@ -188,6 +189,13 @@ async def _shutdown_wcdb_realtime() -> None:
         CHAT_REALTIME_AUTOSYNC.stop()
     except Exception:
         pass
+    
+    # Uninstall img_helper hook if enabled
+    try:
+        IMG_HELPER.disable()
+    except Exception:
+        pass
+
     close_ok = False
     lock_timeout_s: float | None = 0.2
     try:
diff --git a/src/wechat_decrypt_tool/img_helper.py b/src/wechat_decrypt_tool/img_helper.py
new file mode 100644
index 0000000..2e59413
--- /dev/null
+++ b/src/wechat_decrypt_tool/img_helper.py
@@ -0,0 +1,111 @@
+import ctypes
+import os
+from pathlib import Path
+from typing import Optional
+from .logging_config import get_logger
+
+logger = get_logger(__name__)
+
+class ImgHelper:
+    def __init__(self):
+        self._lib: Optional[ctypes.CDLL] = None
+        self._enabled = False
+        self._lock = __import__("threading").Lock()
+
+    def _resolve_dll_path(self) -> Path:
+        # 1. Default (source code layout)
+        base = Path(__file__).resolve().parent
+        path = base / "native" / "img_helper.dll"
+        if path.exists():
+            return path
+        
+        # 2. Frozen (bundled exe)
+        import sys
+        if getattr(sys, "frozen", False):
+            exe_dir = Path(sys.executable).resolve().parent
+            # Try native subfolder or same folder as exe
+            for p in [exe_dir / "native" / "img_helper.dll", exe_dir / "img_helper.dll"]:
+                if p.exists():
+                    return p
+        
+        # 3. Current working directory
+        for p in [Path.cwd() / "native" / "img_helper.dll", Path.cwd() / "img_helper.dll"]:
+            if p.exists():
+                return p
+        
+        return path # Fallback to default for error message
+
+    def _load_lib(self):
+        if self._lib is not None:
+            return self._lib
+        
+        dll_path = self._resolve_dll_path()
+        if not dll_path.exists():
+            raise FileNotFoundError(f"Missing img_helper.dll at: {dll_path}")
+            
+        try:
+            # On Windows, ensure the DLL's directory is in the search path for dependencies
+            if hasattr(os, 'add_dll_directory'):
+                try:
+                    os.add_dll_directory(str(dll_path.parent))
+                except Exception:
+                    pass
+                    
+            lib = ctypes.CDLL(str(dll_path))
+            
+            lib.InitImgHelper.argtypes = [ctypes.c_uint32]
+            lib.InitImgHelper.restype = ctypes.c_bool
+            
+            lib.UninstallImgHelper.argtypes = []
+            lib.UninstallImgHelper.restype = None
+            
+            lib.GetImgHelperError.argtypes = []
+            lib.GetImgHelperError.restype = ctypes.c_char_p
+            
+            self._lib = lib
+            return lib
+        except Exception as e:
+            logger.error(f"Failed to load img_helper.dll: {e}")
+            raise
+
+    def enable(self, pid: int) -> tuple[bool, str]:
+        with self._lock:
+            try:
+                lib = self._load_lib()
+                if self._enabled:
+                    # If already enabled, we uninstall first to be safe as per DLL docs suggestion
+                    # about being designed to hook one process at a time.
+                    lib.UninstallImgHelper()
+                
+                if lib.InitImgHelper(pid):
+                    self._enabled = True
+                    logger.info(f"ImgHelper hook applied to PID {pid}")
+                    return True, "Success"
+                else:
+                    err_ptr = lib.GetImgHelperError()
+                    err_msg = err_ptr.decode('utf-8', errors='ignore') if err_ptr else "Unknown error"
+                    logger.error(f"ImgHelper hook failed: {err_msg}")
+                    return False, err_msg
+            except Exception as e:
+                logger.error(f"ImgHelper enable exception: {e}")
+                return False, str(e)
+
+    def disable(self) -> bool:
+        with self._lock:
+            if not self._enabled:
+                return True
+            try:
+                lib = self._load_lib()
+                lib.UninstallImgHelper()
+                self._enabled = False
+                logger.info("ImgHelper hook uninstalled")
+                return True
+            except Exception as e:
+                logger.error(f"Failed to uninstall img helper: {e}")
+                return False
+
+    @property
+    def is_enabled(self) -> bool:
+        return self._enabled
+
+IMG_HELPER = ImgHelper()
diff --git a/src/wechat_decrypt_tool/native/img_helper.dll b/src/wechat_decrypt_tool/native/img_helper.dll
new file mode 100644
index 0000000..b4ca9e5
Binary files /dev/null and b/src/wechat_decrypt_tool/native/img_helper.dll differ
diff --git a/src/wechat_decrypt_tool/routers/system.py b/src/wechat_decrypt_tool/routers/system.py
index eabd9bd..10aca8e 100644
--- a/src/wechat_decrypt_tool/routers/system.py
+++ b/src/wechat_decrypt_tool/routers/system.py
@@ -1,7 +1,9 @@
-from fastapi import APIRouter
+from fastapi import APIRouter, HTTPException
 from pydantic import BaseModel
 import asyncio
 from concurrent.futures import ThreadPoolExecutor
+from ..img_helper import IMG_HELPER
+from .wechat_detection import check_wechat_status
 
 router = APIRouter()
 
@@ -32,4 +34,35 @@ async def pick_directory(title: str = "请选择目录", initial_dir: str = ""):
         # 在子线程中执行 GUI 操作
         folder_path = await loop.run_in_executor(pool, _open_folder_dialog, title, initial_dir)
 
-    return {"path": folder_path}
\ No newline at end of file
+    return {"path": folder_path}
+
+
+@router.get("/api/system/img_helper/status", summary="获取大图下载辅助插件状态")
+async def get_img_helper_status():
+    return {
+        "enabled": IMG_HELPER.is_enabled
+    }
+
+
+class ImgHelperToggleRequest(BaseModel):
+    enabled: bool
+
+
+@router.post("/api/system/img_helper/toggle", summary="开启/关闭大图下载辅助插件")
+async def toggle_img_helper(req: ImgHelperToggleRequest):
+    if not req.enabled:
+        IMG_HELPER.disable()
+        return {"status": "success", "enabled": False}
+    
+    # Attempt to enable
+    status_res = await check_wechat_status()
+    wx_status = status_res.get("wx_status", {})
+    if not wx_status.get("is_running") or not wx_status.get("pid"):
+        raise HTTPException(status_code=400, detail="未检测到微信正在运行，请先打开微信再尝试！")
+    
+    pid = wx_status["pid"]
+    ok, err = IMG_HELPER.enable(pid)
+    if not ok:
+        raise HTTPException(status_code=500, detail=f"开启失败: {err}")
+    
+    return {"status": "success", "enabled": True}
\ No newline at end of file