diff --git a/frontend/app.html b/frontend/app.html
index cd2992e..68a10bf 100644
--- a/frontend/app.html
+++ b/frontend/app.html
@@ -1693,9 +1693,10 @@
             <div v-for="file in files" :key="file.name" class="file-grid-item" @click="handleFileClick(file)" @contextmenu.prevent.stop="showFileContextMenu(file, $event)" @touchstart="handleLongPressStart(file, $event)" @touchmove="handleLongPressMove($event)" @touchend="handleLongPressEnd" @touchcancel="handleLongPressEnd" @selectstart.prevent @dragstart.prevent>
               <div class="file-icon">
                 <!-- 图片缩略图 -->
-                <img v-if="file.name.match(/\.(jpg|jpeg|png|gif|bmp|svg|webp)$/i) && getThumbnailUrl(file)" 
+                <img v-if="file.name.match(/\.(jpg|jpeg|png|gif|bmp|svg|webp)$/i) && getThumbnailUrl(file) && !isThumbnailLoadFailed(file)" 
                      :src="getThumbnailUrl(file)" 
                      :alt="file.name"
+                     @error="markThumbnailLoadFailed(file)"
                      class="file-thumbnail">
                 <!-- 视频图标（不预加载，避免慢） -->
                 <div v-else-if="file.name.match(/\.(mp4|avi|mov|wmv|flv|mkv|webm)$/i)" 
@@ -1742,9 +1743,10 @@
                   <td class="file-list-name-cell">
                     <div class="file-list-name-wrap">
                     <!-- 图片缩略图 -->
-                    <img v-if="file.name.match(/\.(jpg|jpeg|png|gif|bmp|svg|webp)$/i) && getThumbnailUrl(file)" 
+                    <img v-if="file.name.match(/\.(jpg|jpeg|png|gif|bmp|svg|webp)$/i) && getThumbnailUrl(file) && !isThumbnailLoadFailed(file)" 
                          :src="getThumbnailUrl(file)" 
                          :alt="file.name"
+                         @error="markThumbnailLoadFailed(file)"
                          class="file-list-thumb">
                     <!-- 视频图标 -->
                     <div v-else-if="file.name.match(/\.(mp4|avi|mov|wmv|flv|mkv|webm)$/i)" 
diff --git a/frontend/app.js b/frontend/app.js
index eef63bb..7a2fc6f 100644
--- a/frontend/app.js
+++ b/frontend/app.js
@@ -260,6 +260,7 @@ createApp({
       currentMediaUrl: '',
       currentMediaName: '',
       currentMediaType: '', // 'image', 'video', 'audio'
+      thumbnailLoadErrors: {}, // 缩略图加载失败标记（按文件路径）
       longPressDuration: 420, // 长按时间（毫秒）
       // 管理员编辑用户存储权限
       showEditStorageModal: false,
@@ -1474,6 +1475,7 @@ handleDragLeave(e) {
 
         if (response.data.success) {
           this.files = response.data.items;
+          this.thumbnailLoadErrors = {};
 
           // 更新存储类型信息
           if (response.data.storageType) {
@@ -1886,6 +1888,25 @@ handleDragLeave(e) {
 
     // ===== 媒体预览功能 =====
 
+    getCurrentFilePath(file) {
+      if (!file || !file.name) return '';
+      return this.currentPath === '/' ? `/${file.name}` : `${this.currentPath}/${file.name}`;
+    },
+
+    isThumbnailLoadFailed(file) {
+      const filePath = this.getCurrentFilePath(file);
+      return !!(filePath && this.thumbnailLoadErrors[filePath]);
+    },
+
+    markThumbnailLoadFailed(file) {
+      const filePath = this.getCurrentFilePath(file);
+      if (!filePath || this.thumbnailLoadErrors[filePath]) return;
+      this.thumbnailLoadErrors = {
+        ...this.thumbnailLoadErrors,
+        [filePath]: true
+      };
+    },
+
     // 获取媒体文件URL（OSS直连或后端代理）
     async getMediaUrl(file) {
       const filePath = this.currentPath === '/'
@@ -1922,12 +1943,18 @@ handleDragLeave(e) {
 
       if (!isImage && !isVideo) return null;
 
+      const downloadQuota = Number(this.user?.download_traffic_quota);
+      const downloadUsed = Number(this.user?.download_traffic_used || 0);
+      if (Number.isFinite(downloadQuota) && downloadQuota >= 0) {
+        if (downloadQuota === 0 || downloadUsed >= downloadQuota) {
+          return null;
+        }
+      }
+
       // 本地存储模式：返回同步的下载 URL
       // OSS 模式下缩略图功能暂不支持（需要预签名 URL，建议点击文件预览）
       if (this.storageType !== 'oss') {
-        const filePath = this.currentPath === '/'
-          ? `/${file.name}`
-          : `${this.currentPath}/${file.name}`;
+        const filePath = this.getCurrentFilePath(file);
         return `${this.apiBase}/api/files/download?path=${encodeURIComponent(filePath)}`;
       }