diff --git a/webapp/services/MissionService.php b/webapp/services/MissionService.php
index ae5591c8..2021a370 100644
--- a/webapp/services/MissionService.php
+++ b/webapp/services/MissionService.php
@@ -565,13 +565,12 @@ class MissionService extends BaseService {
         }
 
         foreach (array_rand($metas, count($metas)) as $key) {
+            $meta = $metas[$key];
             if (count($this->offerRewartdMission['missions']) >=
                 $wantedRefreshMissionNum) {
                 break;
             }
-            $meta = $metas[$key];
-            $found = false;
-            if (!$found) {
+            if (!$this->inOfferRewardMission($meta['id'])) {
                 array_push($this->offerRewartdMission['missions'],
                            array(
                                'mission_id' => $meta['id'],
@@ -876,4 +875,14 @@ class MissionService extends BaseService {
         return count($missions);
     }
 
+    private function inOfferRewardMission($missionId)
+    {
+        foreach ($this->offerRewartdMission['missions'] as $mission) {
+            if ($mission['mission_id'] == $missionId) {
+                return true;
+            }
+        }
+        return false;
+    }
+
 }