diff --git a/configs/datasets/mot.yml b/configs/datasets/mot.yml
index e6e8ee7196f6bfb8e7ee6b4e3018ef3d8a176940..26b30c00be486b22f3e37ef824a382ce1a2d614d 100644
--- a/configs/datasets/mot.yml
+++ b/configs/datasets/mot.yml
@@ -19,13 +19,15 @@ TrainDataset:
     image_lists: ['mot17.train', 'caltech.all', 'cuhksysu.train', 'prw.train', 'citypersons.train', 'eth.train']
     data_fields: ['image', 'gt_bbox', 'gt_class', 'gt_ide']
 
+# for detection or reid evaluation, no use in MOT evaluation
 EvalDataset:
   !MOTDataSet
     dataset_dir: dataset/mot
-    image_lists: ['citypersons.val', 'caltech.val'] # for detection
-    # image_lists: ['caltech.10k.val', 'cuhksysu.val', 'prw.val'] # for reid
+    image_lists: ['citypersons.val', 'caltech.val'] # for detection evaluation
+    # image_lists: ['caltech.10k.val', 'cuhksysu.val', 'prw.val'] # for reid evaluation
     data_fields: ['image', 'gt_bbox', 'gt_class', 'gt_ide']
 
+# for detection inference, no use in MOT inference
 TestDataset:
   !ImageFolder
     dataset_dir: dataset/mot
diff --git a/ppdet/data/source/mot.py b/ppdet/data/source/mot.py
index a8a11dc91d7f8d974d71b3207fd8686c03839625..1e61f440812f905b0f8eeb539530765cea84e6f3 100644
--- a/ppdet/data/source/mot.py
+++ b/ppdet/data/source/mot.py
@@ -124,28 +124,6 @@ class MOTDataSet(DetDataset):
                 self.img_start_index[data_name] = img_index
                 img_index += len(self.img_files[data_name])
 
-            # check data directory, images and labels_with_ids
-            if len(self.img_files[data_name]) == 0:
-                continue
-            else:
-                # self.img_files[data_name] each line following this: 
-                # {self.dataset_dir}/MOT17/images/...
-                first_path = self.img_files[data_name][0]
-                data_dir = first_path.replace(self.dataset_dir,
-                                              '').split('/')[1]
-                data_dir = os.path.join(self.dataset_dir, data_dir)
-                assert os.path.exists(data_dir), \
-                    "The data directory {} does not exist.".format(data_dir)
-
-                data_dir_images = os.path.join(data_dir, 'images')
-                assert os.path.exists(data_dir), \
-                    "The data images directory {} does not exist.".format(data_dir_images)
-
-                data_dir_labels_with_ids = os.path.join(data_dir,
-                                                        'labels_with_ids')
-                assert os.path.exists(data_dir), \
-                    "The data labels directory {} does not exist.".format(data_dir_labels_with_ids)
-
             # record label_files
             self.label_files[data_name] = [
                 x.replace('images', 'labels_with_ids').replace(
diff --git a/ppdet/data/transform/mot_operators.py b/ppdet/data/transform/mot_operators.py
index 54f6438eb20a4e9adaf5cf3d476977eaa765cb88..4944ec6fa4b1e1652f794da7cf218d81aa103c6d 100644
--- a/ppdet/data/transform/mot_operators.py
+++ b/ppdet/data/transform/mot_operators.py
@@ -25,6 +25,7 @@ from numbers import Integral
 import cv2
 import copy
 import numpy as np
+import random
 import math
 
 from .operators import BaseOperator, register_op