diff --git a/tests/test_detection_data/test_datasets/test_few_shot_coco_dataset.py b/tests/test_detection_data/test_datasets/test_few_shot_coco_dataset.py
index 0711cc8..ecc8da8 100644
--- a/tests/test_detection_data/test_datasets/test_few_shot_coco_dataset.py
+++ b/tests/test_detection_data/test_datasets/test_few_shot_coco_dataset.py
@@ -1,5 +1,6 @@
 # Copyright (c) OpenMMLab. All rights reserved.
 import copy
+import os
 import tempfile
 
 import numpy as np
@@ -144,10 +145,10 @@ def test_few_shot_coco_dataset():
 
     # test save and load dataset
     with tempfile.TemporaryDirectory() as tmpdir:
-        dataset.save_data_infos(tmpdir + 'ann.json')
+        dataset.save_data_infos(tmpdir + f'{os.sep}ann.json')
         data_config['ann_cfg'] = [{
             'type': 'saved_dataset',
-            'ann_file': tmpdir + 'ann.json'
+            'ann_file': tmpdir + f'{os.sep}ann.json'
         }]
         dataset = FewShotCocoDataset(**data_config)
         count = 0
diff --git a/tests/test_detection_data/test_datasets/test_few_shot_voc_dataset.py b/tests/test_detection_data/test_datasets/test_few_shot_voc_dataset.py
index ccf955a..6ca11d8 100644
--- a/tests/test_detection_data/test_datasets/test_few_shot_voc_dataset.py
+++ b/tests/test_detection_data/test_datasets/test_few_shot_voc_dataset.py
@@ -1,5 +1,6 @@
 # Copyright (c) OpenMMLab. All rights reserved.
 import copy
+import os
 import tempfile
 
 import numpy as np
@@ -108,10 +109,10 @@ def test_few_shot_voc_dataset():
         dataset.data_infos[1]['ann']['bboxes_ignore'] = np.array(
             [[11, 11, 100, 100]])
         dataset.data_infos[1]['ann']['labels_ignore'] = np.array([0])
-        dataset.save_data_infos(tmpdir + 'ann.json')
+        dataset.save_data_infos(tmpdir + f'{os.sep}ann.json')
         data_config['ann_cfg'] = [{
             'type': 'saved_dataset',
-            'ann_file': tmpdir + 'ann.json'
+            'ann_file': tmpdir + f'{os.sep}ann.json'
         }]
         dataset = FewShotVOCDataset(**data_config)
         count = 0
diff --git a/tests/test_detection_data/test_datasets/test_nway_kshot_dataset.py b/tests/test_detection_data/test_datasets/test_nway_kshot_dataset.py
index ae663cd..eaf6762 100644
--- a/tests/test_detection_data/test_datasets/test_nway_kshot_dataset.py
+++ b/tests/test_detection_data/test_datasets/test_nway_kshot_dataset.py
@@ -1,4 +1,5 @@
 # Copyright (c) OpenMMLab. All rights reserved.
+import os
 import tempfile
 
 import numpy as np
@@ -85,4 +86,4 @@ def test_nway_kshot_dataset():
                 assert count <= 1
         # test save dataset
         with tempfile.TemporaryDirectory() as tmpdir:
-            nway_kshot_dataset.save_data_infos(tmpdir + 'ann.json')
+            nway_kshot_dataset.save_data_infos(tmpdir + f'{os.sep}ann.json')
diff --git a/tests/test_detection_data/test_datasets/test_query_aware_dataset.py b/tests/test_detection_data/test_datasets/test_query_aware_dataset.py
index 798f795..816bd33 100644
--- a/tests/test_detection_data/test_datasets/test_query_aware_dataset.py
+++ b/tests/test_detection_data/test_datasets/test_query_aware_dataset.py
@@ -1,4 +1,5 @@
 # Copyright (c) OpenMMLab. All rights reserved.
+import os
 import tempfile
 
 import numpy as np
@@ -115,4 +116,4 @@ def test_query_aware_dataset():
 
     # test save dataset
     with tempfile.TemporaryDirectory() as tmpdir:
-        query_aware_dataset.save_data_infos(tmpdir + 'ann.json')
+        query_aware_dataset.save_data_infos(tmpdir + f'{os.sep}ann.json')
diff --git a/tests/test_detection_data/test_datasets/test_two_branch_dataset.py b/tests/test_detection_data/test_datasets/test_two_branch_dataset.py
index 5bf24e4..8632ced 100644
--- a/tests/test_detection_data/test_datasets/test_two_branch_dataset.py
+++ b/tests/test_detection_data/test_datasets/test_two_branch_dataset.py
@@ -1,4 +1,5 @@
 # Copyright (c) OpenMMLab. All rights reserved.
+import os
 import tempfile
 
 from mmdet.apis import set_random_seed
@@ -45,4 +46,4 @@ def test_two_branch_dataset():
     assert len(two_branch_dataset) == 25
     # test save dataset
     with tempfile.TemporaryDirectory() as tmpdir:
-        two_branch_dataset.save_data_infos(tmpdir + 'ann.json')
+        two_branch_dataset.save_data_infos(tmpdir + f'{os.sep}ann.json')