diff --git a/src/SKIT.FlurlHttpClient.Wechat.TenpayV3/Constants/FormDataFields.cs b/src/SKIT.FlurlHttpClient.Wechat.TenpayV3/Constants/FormDataFields.cs
new file mode 100644
index 00000000..ae5948f0
--- /dev/null
+++ b/src/SKIT.FlurlHttpClient.Wechat.TenpayV3/Constants/FormDataFields.cs
@@ -0,0 +1,9 @@
+using System;
+
+namespace SKIT.FlurlHttpClient.Wechat.TenpayV3.Constants
+{
+    internal static class FormDataFields
+    {
+        public const string FORMDATA_META = "meta";
+    }
+}
diff --git a/src/SKIT.FlurlHttpClient.Wechat.TenpayV3/Extensions/WechatTenpayClientExecuteMarketingMediaExtensions.cs b/src/SKIT.FlurlHttpClient.Wechat.TenpayV3/Extensions/WechatTenpayClientExecuteMarketingMediaExtensions.cs
index 01ac722e..40d32987 100644
--- a/src/SKIT.FlurlHttpClient.Wechat.TenpayV3/Extensions/WechatTenpayClientExecuteMarketingMediaExtensions.cs
+++ b/src/SKIT.FlurlHttpClient.Wechat.TenpayV3/Extensions/WechatTenpayClientExecuteMarketingMediaExtensions.cs
@@ -51,7 +51,7 @@ namespace SKIT.FlurlHttpClient.Wechat.TenpayV3
             using var fileContent = new ByteArrayContent(request.FileBytes);
             using var metaContent = new ByteArrayContent(Encoding.UTF8.GetBytes(client.JsonSerializer.Serialize(request)));
             using var httpContent = new MultipartFormDataContent(boundary);
-            httpContent.Add(metaContent, "\"meta\"");                                                                  // NOTICE: meta 必须要加双引号
+            httpContent.Add(metaContent, "\"" + Constants.FormDataFields.FORMDATA_META + "\"");                        // NOTICE: meta 必须要加双引号
             httpContent.Add(fileContent, "\"file\"", "\"" + request.FileName + "\"");                                  // NOTICE: file 必须要加双引号
             httpContent.Headers.ContentType = MediaTypeHeaderValue.Parse("multipart/form-data; boundary=" + boundary); // NOTICE: boundary 不能加引号
             metaContent.Headers.ContentType = MediaTypeHeaderValue.Parse("application/json");
diff --git a/src/SKIT.FlurlHttpClient.Wechat.TenpayV3/Extensions/WechatTenpayClientExecuteMerchantMediaExtensions.cs b/src/SKIT.FlurlHttpClient.Wechat.TenpayV3/Extensions/WechatTenpayClientExecuteMerchantMediaExtensions.cs
index c2443b52..e553bb0e 100644
--- a/src/SKIT.FlurlHttpClient.Wechat.TenpayV3/Extensions/WechatTenpayClientExecuteMerchantMediaExtensions.cs
+++ b/src/SKIT.FlurlHttpClient.Wechat.TenpayV3/Extensions/WechatTenpayClientExecuteMerchantMediaExtensions.cs
@@ -51,7 +51,7 @@ namespace SKIT.FlurlHttpClient.Wechat.TenpayV3
             using var fileContent = new ByteArrayContent(request.FileBytes);
             using var metaContent = new StringContent(client.JsonSerializer.Serialize(request), Encoding.UTF8, "application/json");
             using var httpContent = new MultipartFormDataContent(boundary);
-            httpContent.Add(metaContent, "\"meta\"");                                                                  // NOTICE: meta 必须要加双引号
+            httpContent.Add(metaContent, "\"" + Constants.FormDataFields.FORMDATA_META + "\"");                        // NOTICE: meta 必须要加双引号
             httpContent.Add(fileContent, "\"file\"", "\"" + request.FileName + "\"");                                  // NOTICE: file 必须要加双引号
             httpContent.Headers.ContentType = MediaTypeHeaderValue.Parse("multipart/form-data; boundary=" + boundary); // NOTICE: boundary 不能加引号
             metaContent.Headers.ContentType = MediaTypeHeaderValue.Parse("application/json");
diff --git a/src/SKIT.FlurlHttpClient.Wechat.TenpayV3/Extensions/WechatTenpayClientExecuteMerchantServiceExtensions.cs b/src/SKIT.FlurlHttpClient.Wechat.TenpayV3/Extensions/WechatTenpayClientExecuteMerchantServiceExtensions.cs
index d71f5e8a..4ed6dc88 100644
--- a/src/SKIT.FlurlHttpClient.Wechat.TenpayV3/Extensions/WechatTenpayClientExecuteMerchantServiceExtensions.cs
+++ b/src/SKIT.FlurlHttpClient.Wechat.TenpayV3/Extensions/WechatTenpayClientExecuteMerchantServiceExtensions.cs
@@ -262,7 +262,7 @@ namespace SKIT.FlurlHttpClient.Wechat.TenpayV3
             using var fileContent = new ByteArrayContent(request.FileBytes);
             using var metaContent = new ByteArrayContent(Encoding.UTF8.GetBytes(client.JsonSerializer.Serialize(request)));
             using var httpContent = new MultipartFormDataContent(boundary);
-            httpContent.Add(metaContent, "\"meta\"");                                                                  // NOTICE: meta 必须要加双引号
+            httpContent.Add(metaContent, "\"" + Constants.FormDataFields.FORMDATA_META + "\"");                        // NOTICE: meta 必须要加双引号
             httpContent.Add(fileContent, "\"file\"", "\"" + request.FileName + "\"");                                  // NOTICE: file 必须要加双引号
             httpContent.Headers.ContentType = MediaTypeHeaderValue.Parse("multipart/form-data; boundary=" + boundary); // NOTICE: boundary 不能加引号
             metaContent.Headers.ContentType = MediaTypeHeaderValue.Parse("application/json");
diff --git a/src/SKIT.FlurlHttpClient.Wechat.TenpayV3/Interceptors/WechatTenpayAuthenticator.cs b/src/SKIT.FlurlHttpClient.Wechat.TenpayV3/Interceptors/WechatTenpayAuthenticator.cs
index ffd13c06..689e5209 100644
--- a/src/SKIT.FlurlHttpClient.Wechat.TenpayV3/Interceptors/WechatTenpayAuthenticator.cs
+++ b/src/SKIT.FlurlHttpClient.Wechat.TenpayV3/Interceptors/WechatTenpayAuthenticator.cs
@@ -33,10 +33,10 @@ namespace SKIT.FlurlHttpClient.Wechat.TenpayV3.Interceptors
 
             if (flurlCall.HttpRequestMessage.Content is MultipartFormDataContent)
             {
-                // NOTICE: multipart/form-data 文件上传请求的待签名参数需特殊处理。
+                // NOTICE: multipart/form-data 文件上传请求的待签名参数需特殊处理
                 var httpContent = (MultipartFormDataContent)flurlCall.HttpRequestMessage.Content;
                 body = httpContent
-                    .Where(e => "meta".Equals(e.Headers.ContentDisposition?.Name?.Trim('\"')))
+                    .Where(e => Constants.FormDataFields.FORMDATA_META.Equals(e.Headers.ContentDisposition?.Name?.Trim('\"')))
                     .Select(e => e.ReadAsStringAsync().ConfigureAwait(false).GetAwaiter().GetResult())
                     .Single();
             }