diff --git a/ppdet/utils/coco_eval.py b/ppdet/utils/coco_eval.py
index 1d0695220534b46de0e818dc5418e4562d074586..a4df01b3c1cc411a1fed2ae1f15f21c5f13af894 100644
--- a/ppdet/utils/coco_eval.py
+++ b/ppdet/utils/coco_eval.py
@@ -311,7 +311,9 @@ def bbox2out(results, clsid2catid, is_bbox_normalized=False):
             for j in range(num):
                 dt = bboxes[k]
                 clsid, score, xmin, ymin, xmax, ymax = dt.tolist()
-                if clsid < 0: continue
+                if clsid < 0:
+                    k += 1  #to continue to handle the subsequent bbox of current image
+                    continue
                 catid = (clsid2catid[int(clsid)])
 
                 if is_bbox_normalized: