diff --git a/ppocr/data/cls/dataset_traversal.py b/ppocr/data/cls/dataset_traversal.py
index 01f8c89c..ea05b859 100755
--- a/ppocr/data/cls/dataset_traversal.py
+++ b/ppocr/data/cls/dataset_traversal.py
@@ -74,7 +74,7 @@ class SimpleReader(object):
 
         def get_device_num():
             if self.use_gpu:
-                gpus = os.environ.get("CUDA_VISIBLE_DEVICES", 1)
+                gpus = os.environ.get("CUDA_VISIBLE_DEVICES", "1")
                 gpu_num = len(gpus.split(','))
                 return gpu_num
             else: