diff --git a/backend/storage.js b/backend/storage.js
index e1fc94a..8014a8b 100644
--- a/backend/storage.js
+++ b/backend/storage.js
@@ -321,6 +321,13 @@ class LocalStorageClient {
     // 更新内存中的值
     this.user.local_storage_used = newUsed;
   }
+
+  /**
+   * 格式化文件大小
+   */
+  formatSize(bytes) {
+    return formatFileSize(bytes);
+  }
 }
 
 // ===== OSS存储客户端 =====
@@ -538,7 +545,7 @@ class OssStorageClient {
       });
 
       await this.s3Client.send(command);
-      console.log(`[OSS存储] 上传成功: ${key} (${this.formatSize(fileSize)})`);
+      console.log(`[OSS存储] 上传成功: ${key} (${formatFileSize(fileSize)})`);
 
       // 关闭流
       if (!fileStream.destroyed) {
@@ -744,7 +751,6 @@ class OssStorageClient {
       // OSS 中文件夹通过以斜杠结尾的空对象模拟
       const folderKey = key.endsWith('/') ? key : `${key}/`;
 
-      const { PutObjectCommand } = require('@aws-sdk/client-s3');
       const command = new PutObjectCommand({
         Bucket: bucket,
         Key: folderKey,
@@ -788,6 +794,13 @@ class OssStorageClient {
     return `${baseUrl}/${key}`;
   }
 
+  /**
+   * 格式化文件大小
+   */
+  formatSize(bytes) {
+    return formatFileSize(bytes);
+  }
+
   /**
    * 关闭连接（S3Client 无需显式关闭）
    */