diff --git a/library/think/Request.php b/library/think/Request.php
index 93fbb95b7e6746d7ec4cc6bfb6b92c9f38396a4d..c45b978eb585b954ee8c56d1fd2117f1908623d5 100644
--- a/library/think/Request.php
+++ b/library/think/Request.php
@@ -733,9 +733,9 @@ class Request
         }
 
         foreach ($this->mimeType as $key => $val) {
-            $array = explode(',', $val);
-            foreach ($array as $k => $v) {
-                if (stristr($accept, $v)) {
+            $array = array_flip(explode(',', $val));
+            foreach ($accept as $v) {
+                if (isset($array[$v])) {
                     return $key;
                 }
             }