diff --git a/paddle2onnx/legacy/op_mapper/detection/multiclass_nms.py b/paddle2onnx/legacy/op_mapper/detection/multiclass_nms.py
index 1445bb81b..9e57ff8fc 100755
--- a/paddle2onnx/legacy/op_mapper/detection/multiclass_nms.py
+++ b/paddle2onnx/legacy/op_mapper/detection/multiclass_nms.py
@@ -74,6 +74,10 @@ def opset_10(cls, graph, node, **kw):
                     outputs=num_class,
                     axis=0)
             bbox_ids = []
+            if not isinstance(scores_list, list):
+                scores_list = [scores_list]
+            if not isinstance(bboxes_list, list):
+                bboxes_list = [bboxes_list]
             for i in range(num_class):
                 bbox_id = cls.nms(graph,
                                   node,