diff --git a/src/middleware/http.ts b/src/middleware/http.ts
index fb07ba1c21834b196d14ae77229acbb8774ade57..549e76c6b6a4ab575d998697dbad1bddc1639406 100644
--- a/src/middleware/http.ts
+++ b/src/middleware/http.ts
@@ -17,6 +17,7 @@ const isObject = (field: unknown): field is Data => typeof field !== 'string'
 
 const CONTENT_TYPE = 'content-type'
 const JSON_TYPE = 'application/json'
+const STRING_TYPE = 'text/plain'
 const FORM_TYPE = 'application/x-www-form-urlencoded'
 
 function initContextType(headers: Data) {
@@ -98,20 +99,42 @@ export async function http(ctx: Context, next: Next) {
       if (ctx.config.debug === true) {
         ;(ret as any).stack = e.stack || ''
       }
-      return (ctx.body = {
-        mpserverlessComposedResponse: true, // aliyun
-        statusCode: 400,
-        headers: contentTypeHeader,
-        body: JSON.stringify(ret),
-      })
+      const res = {
+		mpserverlessComposedResponse: true, // aliyun
+		statusCode: 400,
+		headers: contentTypeHeader
+	  }
+	  if( typeof(ret) == 'string' )
+	  {
+		res.body = ret
+		res.headers[CONTENT_TYPE] = STRING_TYPE
+	  }
+	  else 
+      {
+        res.headers[CONTENT_TYPE] = JSON_TYPE
+        res.body = JSON.stringify(ret)
+      }
+      return (ctx.body = body)
     }
     const contextType = ctx.headers[CONTENT_TYPE] || JSON_TYPE
-    ctx.body = {
+	
+	const res = {
       mpserverlessComposedResponse: true, // aliyun
-      isBase64Encoded: !!ctx.isBase64Encoded,
+	  isBase64Encoded: !!ctx.isBase64Encoded,
       statusCode: ctx.status,
-      headers: Object.assign(ctx.headers, { [CONTENT_TYPE]: contextType }),
-      body: contextType === JSON_TYPE ? JSON.stringify(ctx.body) : ctx.body,
+	  headers: Object.assign(ctx.headers, { [CONTENT_TYPE]: contextType })
+	}
+	if( typeof(ctx.body) == 'string' )
+	{
+      res.body = ctx.body
+      res.headers[CONTENT_TYPE] = STRING_TYPE
+	}
+	else 
+    {
+      res.headers[CONTENT_TYPE] = JSON_TYPE
+      res.body = JSON.stringify(ctx.body)
     }
+	
+    ctx.body = res
   }
 }