diff --git a/ppdet/data/source/coco.py b/ppdet/data/source/coco.py
index 22a0d7e3a5b22ec9b5df4e3dc18ebbab882be8d1..0833a322797b19554fa6f98da62ea00ac1d49b96 100644
--- a/ppdet/data/source/coco.py
+++ b/ppdet/data/source/coco.py
@@ -14,7 +14,6 @@
 
 import os
 import numpy as np
-from pycocotools.coco import COCO
 
 from .dataset import DataSet
 from ppdet.core.workspace import register, serializable
@@ -75,6 +74,7 @@ class COCODataSet(DataSet):
 
         assert anno_path.endswith('.json'), \
             'invalid coco annotation file: ' + anno_path
+        from pycocotools.coco import COCO
         coco = COCO(anno_path)
         img_ids = coco.getImgIds()
         cat_ids = coco.getCatIds()
diff --git a/ppdet/data/source/dataset.py b/ppdet/data/source/dataset.py
index 9f604fe9ab20c60c3634b25895ac5564b633b6b2..806dd2b12423d6bddd09ba9e50566bb33c1a3bd1 100644
--- a/ppdet/data/source/dataset.py
+++ b/ppdet/data/source/dataset.py
@@ -75,6 +75,8 @@ class DataSet(object):
         return self.cname2cid
 
     def get_anno(self):
+        if self.anno_path is None:
+            return
         return os.path.join(self.dataset_dir, self.anno_path)
 
     def get_imid2path(self):
diff --git a/ppdet/utils/visualizer.py b/ppdet/utils/visualizer.py
index e27bad90b9dbc250bc0962d623565387bb1aa97d..0658c8c355db67aa54c4e461b5eeb40506d668bc 100644
--- a/ppdet/utils/visualizer.py
+++ b/ppdet/utils/visualizer.py
@@ -18,7 +18,6 @@ from __future__ import print_function
 from __future__ import unicode_literals
 
 import numpy as np
-import pycocotools.mask as mask_util
 from PIL import Image, ImageDraw
 
 from .colormap import colormap
@@ -56,6 +55,7 @@ def draw_mask(image, im_id, segms, threshold, alpha=0.7):
         segm, score = dt['segmentation'], dt['score']
         if score < threshold:
             continue
+        import pycocotools.mask as mask_util
         mask = mask_util.decode(segm) * 255
         color_mask = color_list[mask_color_id % len(color_list), 0:3]
         mask_color_id += 1