diff --git a/src/SKIT.FlurlHttpClient.Wechat.TenpayBusiness/Interceptors/WechatTenpayBusinessRequestSigningInterceptor.cs b/src/SKIT.FlurlHttpClient.Wechat.TenpayBusiness/Interceptors/WechatTenpayBusinessRequestSigningInterceptor.cs
index 32c29c68..ae8369a4 100644
--- a/src/SKIT.FlurlHttpClient.Wechat.TenpayBusiness/Interceptors/WechatTenpayBusinessRequestSigningInterceptor.cs
+++ b/src/SKIT.FlurlHttpClient.Wechat.TenpayBusiness/Interceptors/WechatTenpayBusinessRequestSigningInterceptor.cs
@@ -9,6 +9,7 @@ namespace SKIT.FlurlHttpClient.Wechat.TenpayBusiness.Interceptors
 {
     using SKIT.FlurlHttpClient.Internal;
     using SKIT.FlurlHttpClient.Primitives;
+    using SKIT.FlurlHttpClient.Wechat.TenpayBusiness.Constants;
 
     internal class WechatTenpayBusinessRequestSigningInterceptor : HttpInterceptor
     {
@@ -45,39 +46,42 @@ namespace SKIT.FlurlHttpClient.Wechat.TenpayBusiness.Interceptors
             string nonce = Guid.NewGuid().ToString("N");
             string body = string.Empty;
 
-            if (context.FlurlCall.HttpRequestMessage.Content is MultipartFormDataContent formdataContent)
+            if (context.FlurlCall.HttpRequestMessage?.Content is not null)
             {
-                // NOTICE: multipart/form-data 文件上传请求的待签名参数需特殊处理
-                var httpContent = formdataContent.SingleOrDefault(e => Constants.FormDataFields.FORMDATA_META.Equals(e.Headers.ContentDisposition?.Name?.Trim('\"')));
-                if (httpContent is not null)
+                if (context.FlurlCall.HttpRequestMessage.Content is MultipartFormDataContent multipartFormData)
                 {
+                    HttpContent httpContent = multipartFormData.SingleOrDefault(e => FormDataFields.FORMDATA_META.Equals(e.Headers.ContentDisposition?.Name?.Trim('\"')));
+                    if (httpContent is not null)
+                    {
+                        body = await _AsyncEx.RunTaskWithCancellationTokenAsync(httpContent.ReadAsStringAsync(), cancellationToken).ConfigureAwait(false);
+                    }
+                }
+                else if (method != "GET")
+                {
+                    HttpContent httpContent = context.FlurlCall.HttpRequestMessage.Content;
                     body = await _AsyncEx.RunTaskWithCancellationTokenAsync(httpContent.ReadAsStringAsync(), cancellationToken).ConfigureAwait(false);
                 }
             }
-            else
-            {
-                body = context.FlurlCall.RequestBody ?? string.Empty;
-            }
 
-            string plainText = $"{method}\n{url}\n{timestamp}\n{nonce}\n{body}\n";
-            string signText;
+            string signData = $"{method}\n{url}\n{timestamp}\n{nonce}\n{body}\n";
+            string sign;
 
             bool softSignRequired = _enterpriseId is not null && _enterpriseCertSn is not null && _enterpriseCertPk is not null;
-            string? softSignText = null;
+            string? softSign = null;
 
             switch (_signAlg)
             {
-                case Constants.SignAlgorithms.SHA256_WITH_RSA:
+                case SignAlgorithms.SHA256_WITH_RSA:
                     {
                         try
                         {
-                            signText = Utilities.RSAUtility.Sign(_platformCertPk, plainText).Value!;
+                            sign = Utilities.RSAUtility.Sign(_platformCertPk, signData).Value!;
 
                             if (softSignRequired)
                             {
                                 byte[] keyBytes = EncodedString.FromBase64String(_enterpriseCertPk!);
-                                byte[] msgBytes = EncodedString.FromBase64String(signText);
-                                softSignText = EncodedString.ToBase64String(Utilities.RSAUtility.Sign(keyBytes, msgBytes)).Value!;
+                                byte[] msgBytes = EncodedString.FromBase64String(sign);
+                                softSign = EncodedString.ToBase64String(Utilities.RSAUtility.Sign(keyBytes, msgBytes)).Value!;
                             }
                         }
                         catch (Exception ex)
@@ -91,11 +95,11 @@ namespace SKIT.FlurlHttpClient.Wechat.TenpayBusiness.Interceptors
                     throw new WechatTenpayBusinessException($"Failed to sign request. Unsupported signing algorithm: \"{_signAlg}\".");
             }
 
-            context.FlurlCall.Request.WithHeader(HTTP_HEADER_PLATFORM_AUTHORIZATION, $"platform_id=\"{_platformId}\",platform_serial_number=\"{_platformCertSn}\",nonce=\"{nonce}\",timestamp=\"{timestamp}\",signature=\"{signText}\",signature_algorithm=\"{_signAlg}\"");
+            context.FlurlCall.Request.WithHeader(HTTP_HEADER_PLATFORM_AUTHORIZATION, $"platform_id=\"{_platformId}\",platform_serial_number=\"{_platformCertSn}\",nonce=\"{nonce}\",timestamp=\"{timestamp}\",signature=\"{sign}\",signature_algorithm=\"{_signAlg}\"");
 
             if (softSignRequired)
             {
-                context.FlurlCall.Request.WithHeader(HTTP_HEADER_ENTERPRISE_AUTHORIZATION, $"ent_id=\"{_enterpriseId}\",enterprise_serial_number=\"{_enterpriseCertSn}\",signature=\"{softSignText}\",signature_algorithm=\"{_signAlg}\"");
+                context.FlurlCall.Request.WithHeader(HTTP_HEADER_ENTERPRISE_AUTHORIZATION, $"ent_id=\"{_enterpriseId}\",enterprise_serial_number=\"{_enterpriseCertSn}\",signature=\"{softSign}\",signature_algorithm=\"{_signAlg}\"");
             }
         }
     }