diff --git a/docs/changelog.md b/docs/changelog.md
index 3e56586252..069461bdd5 100644
--- a/docs/changelog.md
+++ b/docs/changelog.md
@@ -13,12 +13,14 @@
 - Support training and testing for Spatio-Temporal Action Detection ([#351](https://github.com/open-mmlab/mmaction2/pull/351))
 - Fix CI due to pip upgrade ([#454](https://github.com/open-mmlab/mmaction2/pull/454))
 - Add markdown lint in pre-commit hook ([#255](https://github.com/open-mmlab/mmaction2/pull/225))
-- Use title case in modelzoo statistics. ([#456](https://github.com/open-mmlab/mmaction2/pull/456))
+- Use title case in modelzoo statistics ([#456](https://github.com/open-mmlab/mmaction2/pull/456))
 - Add FAQ documents for easy troubleshooting. ([#413](https://github.com/open-mmlab/mmaction2/pull/413), [#420](https://github.com/open-mmlab/mmaction2/pull/420), [#439](https://github.com/open-mmlab/mmaction2/pull/439))
+- Save best checkpoint during training. ([#464](https://github.com/open-mmlab/mmaction2/pull/464))
 
 **Bug and Typo Fixes**
 
-- Fix typo in default argument of BaseHead. ([#446](https://github.com/open-mmlab/mmaction2/pull/446))
+- Fix typo in default argument of BaseHead ([#446](https://github.com/open-mmlab/mmaction2/pull/446))
+- Fix potential bug about `output_config` overwrite ([#463](https://github.com/open-mmlab/mmaction2/pull/463))
 
 **ModelZoo**
 
diff --git a/mmaction/core/evaluation/eval_hooks.py b/mmaction/core/evaluation/eval_hooks.py
index 40fd5631f2..b4bc037efb 100644
--- a/mmaction/core/evaluation/eval_hooks.py
+++ b/mmaction/core/evaluation/eval_hooks.py
@@ -1,3 +1,4 @@
+import os
 import os.path as osp
 import warnings
 from math import inf
@@ -28,6 +29,8 @@ class EpochEvalHook(Hook):
         interval (int): Evaluation interval (by epochs). Default: 1.
         save_best (bool): Whether to save best checkpoint during evaluation.
             Default: True.
+        save_best_ckpt (bool): Whether to save best checkpoint in work_dir.
+             Default: None.
         key_indicator (str | None): Key indicator to measure the best
             checkpoint during evaluation when ``save_best`` is set to True.
             Options are the evaluation metrics to the test dataset. e.g.,
@@ -53,6 +56,7 @@ def __init__(self,
                  start=None,
                  interval=1,
                  save_best=True,
+                 save_best_ckpt=False,
                  key_indicator='top1_acc',
                  rule=None,
                  **eval_kwargs):
@@ -93,6 +97,8 @@ def __init__(self,
         self.start = start
         self.eval_kwargs = eval_kwargs
         self.save_best = save_best
+        self.save_best_ckpt = save_best_ckpt
+        self._cur_best_ckpt_path = None
         self.key_indicator = key_indicator
         self.rule = rule
 
@@ -132,6 +138,30 @@ def evaluation_flag(self, runner):
                 return False
         return True
 
+    def _do_save_best(self, key_score, json_path, current_ckpt_path, runner):
+        if (self.save_best and self.compare_func(key_score, self.best_score)):
+            self.best_score = key_score
+            self.logger.info(
+                f'Now best checkpoint is epoch_{runner.epoch + 1}.pth')
+            self.best_json['best_score'] = self.best_score
+            self.best_json['best_ckpt'] = current_ckpt_path
+            self.best_json['key_indicator'] = self.key_indicator
+            mmcv.dump(self.best_json, json_path)
+
+            if self.save_best_ckpt:
+                # remove previous best ckpt
+                if self._cur_best_ckpt_path and \
+                   osp.isfile(self._cur_best_ckpt_path):
+                    os.remove(self._cur_best_ckpt_path)
+
+                # save current checkpoint in work_dir
+                # checkpoint name 'best_{best_score}_{epoch_id}.pth'
+                cur_best_ckpt_name = 'best_{:.4f}_{}.pth'.format(
+                    key_score, runner.epoch + 1)
+                runner.save_checkpoint(runner.work_dir, cur_best_ckpt_name)
+                self._cur_best_ckpt_path = osp.join(runner.work_dir,
+                                                    cur_best_ckpt_name)
+
     def after_train_epoch(self, runner):
         """Called after every training epoch to evaluate the results."""
         if not self.evaluation_flag(runner):
@@ -150,14 +180,7 @@ def after_train_epoch(self, runner):
         from mmaction.apis import single_gpu_test
         results = single_gpu_test(runner.model, self.dataloader)
         key_score = self.evaluate(runner, results)
-        if (self.save_best and self.compare_func(key_score, self.best_score)):
-            self.best_score = key_score
-            self.logger.info(
-                f'Now best checkpoint is epoch_{runner.epoch + 1}.pth')
-            self.best_json['best_score'] = self.best_score
-            self.best_json['best_ckpt'] = current_ckpt_path
-            self.best_json['key_indicator'] = self.key_indicator
-            mmcv.dump(self.best_json, json_path)
+        self._do_save_best(key_score, json_path, current_ckpt_path, runner)
 
     def evaluate(self, runner, results):
         """Evaluate the results.
@@ -197,6 +220,8 @@ class DistEpochEvalHook(EpochEvalHook):
         interval (int): Evaluation interval (by epochs). Default: 1.
         save_best (bool): Whether to save best checkpoint during evaluation.
             Default: True.
+        save_best_ckpt (bool): Whether to save best checkpoint in work_dir.
+             Default: None.
         key_indicator (str | None): Key indicator to measure the best
             checkpoint during evaluation when ``save_best`` is set to True.
             Options are the evaluation metrics to the test dataset. e.g.,
@@ -221,6 +246,7 @@ def __init__(self,
                  start=None,
                  interval=1,
                  save_best=True,
+                 save_best_ckpt=False,
                  key_indicator='top1_acc',
                  rule=None,
                  tmpdir=None,
@@ -231,6 +257,7 @@ def __init__(self,
             start=start,
             interval=interval,
             save_best=save_best,
+            save_best_ckpt=save_best_ckpt,
             key_indicator=key_indicator,
             rule=rule,
             **eval_kwargs)
@@ -266,12 +293,4 @@ def after_train_epoch(self, runner):
         if runner.rank == 0:
             print('\n')
             key_score = self.evaluate(runner, results)
-            if (self.save_best and key_score is not None
-                    and self.compare_func(key_score, self.best_score)):
-                self.best_score = key_score
-                self.logger.info(
-                    f'Now best checkpoint is epoch_{runner.epoch + 1}.pth')
-                self.best_json['best_score'] = self.best_score
-                self.best_json['best_ckpt'] = current_ckpt_path
-                self.best_json['key_indicator'] = self.key_indicator
-                mmcv.dump(self.best_json, json_path)
+            self._do_save_best(key_score, json_path, current_ckpt_path, runner)
diff --git a/mmaction/models/builder.py b/mmaction/models/builder.py
index df95a94d40..f7316bd69a 100644
--- a/mmaction/models/builder.py
+++ b/mmaction/models/builder.py
@@ -13,7 +13,7 @@
     # Define an empty registry and building func, so that can import
     DETECTORS = Registry('detector')
 
-    def bulid_detector(cfg, train_cfg, test_cfg):
+    def build_detector(cfg, train_cfg, test_cfg):
         pass
 
 
diff --git a/mmaction/models/heads/roi_head.py b/mmaction/models/heads/roi_head.py
index f94aa85a6a..45a36df528 100644
--- a/mmaction/models/heads/roi_head.py
+++ b/mmaction/models/heads/roi_head.py
@@ -85,5 +85,5 @@ def simple_test_bboxes(self,
             return det_bboxes, det_labels
 else:
     # Just define an empty class, so that __init__ can import it.
-    class AVARoIHead(StandardRoIHead):
+    class AVARoIHead:
         pass
diff --git a/mmaction/models/roi_extractors/single_straight3d.py b/mmaction/models/roi_extractors/single_straight3d.py
index 09d40b1dcf..aafceeaf1d 100644
--- a/mmaction/models/roi_extractors/single_straight3d.py
+++ b/mmaction/models/roi_extractors/single_straight3d.py
@@ -2,7 +2,11 @@
 
 import torch
 import torch.nn as nn
-from mmcv.ops import RoIAlign, RoIPool
+
+try:
+    from mmcv.ops import RoIAlign, RoIPool
+except (ImportError, ModuleNotFoundError):
+    warnings.warn('Please install mmcv-full to use RoIAlign and RoIPool')
 
 try:
     import mmdet  # noqa
diff --git a/tests/test_runtime/test_eval_hook.py b/tests/test_runtime/test_eval_hook.py
index af02be5cbb..e65191c62a 100644
--- a/tests/test_runtime/test_eval_hook.py
+++ b/tests/test_runtime/test_eval_hook.py
@@ -247,8 +247,8 @@ def test_eval_hook():
         assert best_json['key_indicator'] == 'acc'
 
     data_loader = DataLoader(EvalDataset(), batch_size=1)
-    eval_hook = EpochEvalHook(data_loader, key_indicator='acc')
     with tempfile.TemporaryDirectory() as tmpdir:
+        eval_hook = EpochEvalHook(data_loader, key_indicator='acc')
         logger = get_logger('test_eval')
         runner = EpochBasedRunner(
             model=model,
@@ -270,7 +270,8 @@ def test_eval_hook():
 
         resume_from = osp.join(tmpdir, 'latest.pth')
         loader = DataLoader(ExampleDataset(), batch_size=1)
-        eval_hook = EpochEvalHook(data_loader, key_indicator='acc')
+        eval_hook = EpochEvalHook(
+            data_loader, key_indicator='acc', save_best_ckpt=True)
         runner = EpochBasedRunner(
             model=model,
             batch_processor=None,
@@ -289,6 +290,7 @@ def test_eval_hook():
         assert best_json['best_ckpt'] == osp.realpath(real_path)
         assert best_json['best_score'] == 7
         assert best_json['key_indicator'] == 'acc'
+        assert osp.isfile(osp.join(tmpdir, 'best_7.0000_4.pth'))
 
 
 @patch('mmaction.apis.single_gpu_test', MagicMock)
diff --git a/tools/data/activitynet/download_videos.sh b/tools/data/activitynet/download_videos.sh
index 602cf48fcd..5d10a1017d 100644
--- a/tools/data/activitynet/download_videos.sh
+++ b/tools/data/activitynet/download_videos.sh
@@ -4,6 +4,7 @@
 conda env create -f environment.yml
 source activate activitynet
 pip install --upgrade youtube-dl
+pip install mmcv
 
 DATA_DIR="../../../data/ActivityNet"
 python download.py
diff --git a/tools/data/gym/environment.yml b/tools/data/gym/environment.yml
index 86e7e1a24c..b9ecc82678 100644
--- a/tools/data/gym/environment.yml
+++ b/tools/data/gym/environment.yml
@@ -1,4 +1,4 @@
-name: kinetics
+name: gym
 channels:
   - anaconda
   - menpo
diff --git a/tools/test.py b/tools/test.py
index 86315d78f5..b50f8de9cb 100644
--- a/tools/test.py
+++ b/tools/test.py
@@ -102,15 +102,20 @@ def main():
 
     # Load output_config from cfg
     output_config = cfg.get('output_config', {})
-    # Overwrite output_config from args.out
-    output_config = Config._merge_a_into_b(dict(out=args.out), output_config)
+    if args.out:
+        # Overwrite output_config from args.out
+        output_config = Config._merge_a_into_b(
+            dict(out=args.out), output_config)
 
     # Load eval_config from cfg
     eval_config = cfg.get('eval_config', {})
-    # Overwrite eval_config from args.eval
-    eval_config = Config._merge_a_into_b(dict(metrics=args.eval), eval_config)
-    # Add options from args.eval_options
-    eval_config = Config._merge_a_into_b(args.eval_options, eval_config)
+    if args.eval:
+        # Overwrite eval_config from args.eval
+        eval_config = Config._merge_a_into_b(
+            dict(metrics=args.eval), eval_config)
+    if args.eval_options:
+        # Add options from args.eval_options
+        eval_config = Config._merge_a_into_b(args.eval_options, eval_config)
 
     assert output_config or eval_config, \
         ('Please specify at least one operation (save or eval the '