diff --git a/server/MiAssessment/src/MiAssessment.Core/Interfaces/IUploadConfigService.cs b/server/MiAssessment/src/MiAssessment.Core/Interfaces/IUploadConfigService.cs
index 3009c59..e8af761 100644
--- a/server/MiAssessment/src/MiAssessment.Core/Interfaces/IUploadConfigService.cs
+++ b/server/MiAssessment/src/MiAssessment.Core/Interfaces/IUploadConfigService.cs
@@ -16,12 +16,12 @@ public interface IUploadConfigService
 }
 
 /// <summary>
-/// 预签名上传信息（COS POST Object 方式）
+/// 预签名上传信息（COS PUT 预签名URL方式）
 /// </summary>
 public class PresignedUploadInfo
 {
     /// <summary>
-    /// COS上传地址（POST Object 目标URL）
+    /// 预签名上传URL（PUT方式直传）
     /// </summary>
     public string UploadUrl { get; set; } = string.Empty;
 
@@ -30,31 +30,6 @@ public class PresignedUploadInfo
     /// </summary>
     public string FileUrl { get; set; } = string.Empty;
 
-    /// <summary>
-    /// COS对象Key（文件路径）
-    /// </summary>
-    public string Key { get; set; } = string.Empty;
-
-    /// <summary>
-    /// Base64编码的上传策略
-    /// </summary>
-    public string Policy { get; set; } = string.Empty;
-
-    /// <summary>
-    /// SecretId
-    /// </summary>
-    public string SecretId { get; set; } = string.Empty;
-
-    /// <summary>
-    /// 密钥有效时间范围（Unix时间戳格式: startTime;endTime）
-    /// </summary>
-    public string KeyTime { get; set; } = string.Empty;
-
-    /// <summary>
-    /// HMAC-SHA1签名
-    /// </summary>
-    public string Signature { get; set; } = string.Empty;
-
     /// <summary>
     /// URL过期时间（秒）
     /// </summary>
diff --git a/server/MiAssessment/src/MiAssessment.Core/Services/UploadConfigService.cs b/server/MiAssessment/src/MiAssessment.Core/Services/UploadConfigService.cs
index aa22b26..34d18d0 100644
--- a/server/MiAssessment/src/MiAssessment.Core/Services/UploadConfigService.cs
+++ b/server/MiAssessment/src/MiAssessment.Core/Services/UploadConfigService.cs
@@ -11,7 +11,7 @@ namespace MiAssessment.Core.Services;
 
 /// <summary>
 /// 上传配置服务实现
-/// 从Admin库读取COS配置，生成POST Object签名供小程序直传
+/// 从Admin库读取COS配置，生成PUT预签名URL供小程序直传
 /// </summary>
 public class UploadConfigService : IUploadConfigService
 {
@@ -60,53 +60,49 @@ public class UploadConfigService : IUploadConfigService
         var uniqueFileName = $"{timestamp}_{guid}{extension}";
         var objectKey = $"{UploadBasePath}/{datePath}/{uniqueFileName}";
 
-        // 生成POST Object签名信息
-        var host = $"{setting.Bucket}.cos.{setting.Region}.myqcloud.com";
-        var uploadUrl = $"https://{host}";
+        // 生成PUT预签名URL
+        var presignedUrl = GeneratePresignedUrl(setting, objectKey, "PUT", contentType, DefaultExpiresInSeconds);
         var fileUrl = GenerateAccessUrl(setting.Domain!, objectKey);
 
-        var startTime = DateTimeOffset.UtcNow.ToUnixTimeSeconds();
-        var endTime = startTime + DefaultExpiresInSeconds;
-        var keyTime = $"{startTime};{endTime}";
-
-        // 生成policy
-        var policy = GeneratePostPolicy(objectKey, setting.AccessKeyId!, keyTime);
-        var policyBase64 = Convert.ToBase64String(Encoding.UTF8.GetBytes(policy));
-
-        // 生成签名: SignKey -> StringToSign(SHA1 of raw policy) -> Signature
-        var signKey = HmacSha1(setting.AccessKeySecret!, keyTime);
-        var stringToSign = Sha1Hash(policy);
-        var signature = HmacSha1(signKey, stringToSign);
-
-        _logger.LogInformation("生成POST Object签名成功: {ObjectKey}", objectKey);
+        _logger.LogInformation("生成预签名URL成功: {ObjectKey}", objectKey);
 
         return new PresignedUploadInfo
         {
-            UploadUrl = uploadUrl,
+            UploadUrl = presignedUrl,
             FileUrl = fileUrl,
-            Key = objectKey,
-            Policy = policyBase64,
-            SecretId = setting.AccessKeyId!,
-            KeyTime = keyTime,
-            Signature = signature,
             ExpiresIn = DefaultExpiresInSeconds
         };
     }
 
     /// <summary>
-    /// 生成POST Object的policy JSON
-    /// 参考: https://cloud.tencent.com/document/product/436/14690
+    /// 生成腾讯云COS预签名URL（PUT方式）
     /// </summary>
-    private static string GeneratePostPolicy(string objectKey, string secretId, string keyTime)
+    private static string GeneratePresignedUrl(UploadSetting setting, string objectKey, string httpMethod, string contentType, int expiresInSeconds)
     {
-        var expiration = DateTimeOffset.UtcNow.AddSeconds(DefaultExpiresInSeconds).ToString("yyyy-MM-ddTHH:mm:ss.fffZ");
+        var startTime = DateTimeOffset.UtcNow.ToUnixTimeSeconds();
+        var endTime = startTime + expiresInSeconds;
+        var keyTime = $"{startTime};{endTime}";
 
-        // 手动拼接JSON，因为COS要求key中包含连字符（q-sign-algorithm等）
-        var policy = $$"""
-        {"expiration":"{{expiration}}","conditions":[{"q-sign-algorithm":"sha1"},{"q-ak":"{{secretId}}"},{"q-sign-time":"{{keyTime}}"},{"key":"{{objectKey}}"}]}
-        """.Trim();
+        var host = $"{setting.Bucket}.cos.{setting.Region}.myqcloud.com";
+        var urlPath = $"/{objectKey}";
 
-        return policy;
+        // 1. SignKey
+        var signKey = HmacSha1(setting.AccessKeySecret!, keyTime);
+
+        // 2. HttpString
+        var httpString = $"{httpMethod.ToLowerInvariant()}\n{urlPath}\n\nhost={host.ToLowerInvariant()}\n";
+
+        // 3. StringToSign
+        var sha1HttpString = Sha1Hash(httpString);
+        var stringToSign = $"sha1\n{keyTime}\n{sha1HttpString}\n";
+
+        // 4. Signature
+        var signature = HmacSha1(signKey, stringToSign);
+
+        // 5. Authorization
+        var authorization = $"q-sign-algorithm=sha1&q-ak={setting.AccessKeyId}&q-sign-time={keyTime}&q-key-time={keyTime}&q-header-list=host&q-url-param-list=&q-signature={signature}";
+
+        return $"https://{host}{urlPath}?{authorization}";
     }
 
     /// <summary>
diff --git a/uniapp/utils/upload.js b/uniapp/utils/upload.js
index 6e6dbe2..b3782e9 100644
--- a/uniapp/utils/upload.js
+++ b/uniapp/utils/upload.js
@@ -1,7 +1,8 @@
 /**
  * COS直传工具
- * 通过POST Object方式将文件直传到腾讯云COS
- * 参考: https://cloud.tencent.com/document/product/436/14690
+ * 通过PUT预签名URL将文件直传到腾讯云COS
+ * 使用 uni.getFileSystemManager().readFile 读取文件二进制数据
+ * 再通过 uni.request PUT 方式上传（uni.uploadFile 只支持 POST）
  */
 
 import { getPresignedUploadUrl } from '@/api/user.js'
@@ -41,39 +42,39 @@ export async function chooseAndUploadImage(options = {}) {
   const mimeMap = { jpg: 'image/jpeg', jpeg: 'image/jpeg', png: 'image/png', gif: 'image/gif', webp: 'image/webp' }
   const contentType = mimeMap[ext] || 'image/png'
 
-  // 2. 获取POST Object签名信息
+  // 2. 获取预签名URL
   const presignedRes = await getPresignedUploadUrl(fileName, contentType)
   if (!presignedRes || presignedRes.code !== 0 || !presignedRes.data) {
     throw new Error(presignedRes?.message || '获取上传地址失败')
   }
 
-  const { uploadUrl, fileUrl, key, policy, secretId, keyTime, signature } = presignedRes.data
+  const { uploadUrl, fileUrl } = presignedRes.data
 
-  // 3. POST Object方式直传COS
+  // 3. 读取文件二进制数据，然后用PUT方式上传到COS
   await new Promise((resolve, reject) => {
-    uni.uploadFile({
-      url: uploadUrl,
+    uni.getFileSystemManager().readFile({
       filePath: tempFilePath,
-      name: 'file',
-      formData: {
-        'key': key,
-        'policy': policy,
-        'q-sign-algorithm': 'sha1',
-        'q-ak': secretId,
-        'q-key-time': keyTime,
-        'q-sign-time': keyTime,
-        'q-signature': signature
+      success: (readRes) => {
+        // 使用PUT方法上传二进制数据
+        uni.request({
+          url: uploadUrl,
+          method: 'PUT',
+          data: readRes.data,
+          header: {
+            'Content-Type': contentType
+          },
+          success: (res) => {
+            if (res.statusCode === 200) {
+              resolve(res)
+            } else {
+              console.error('COS上传失败:', res.statusCode, res.data)
+              reject(new Error(`上传失败，状态码: ${res.statusCode}`))
+            }
+          },
+          fail: (err) => reject(new Error('上传COS失败: ' + (err.errMsg || '网络错误')))
+        })
       },
-      success: (res) => {
-        // COS POST Object成功返回 200 或 204
-        if (res.statusCode >= 200 && res.statusCode < 300) {
-          resolve(res)
-        } else {
-          console.error('COS上传失败:', res.statusCode, res.data)
-          reject(new Error(`上传失败，状态码: ${res.statusCode}`))
-        }
-      },
-      fail: (err) => reject(new Error(err.errMsg || '上传失败'))
+      fail: (err) => reject(new Error('读取文件失败: ' + err.errMsg))
     })
   })