diff --git a/ppdet/metrics/map_utils.py b/ppdet/metrics/map_utils.py
index f05953e5f1705dcced3fa32c83855844581bae47..9c96b9235f4205279e47ff84006351a012d7bf2d 100644
--- a/ppdet/metrics/map_utils.py
+++ b/ppdet/metrics/map_utils.py
@@ -238,7 +238,7 @@ class DetectionMAP(object):
         """
         self.class_score_poss = [[] for _ in range(self.class_num)]
         self.class_gt_counts = [0] * self.class_num
-        self.mAP = None
+        self.mAP = 0.0
 
     def accumulate(self):
         """