diff --git a/dygraph/ppdet/engine/callbacks.py b/dygraph/ppdet/engine/callbacks.py
index 16d85b4b5fefcbd7aa904d0f3fb9424c1d2df67a..60cde185e109f1f41f57ab9520bb5bcdfbf08e40 100644
--- a/dygraph/ppdet/engine/callbacks.py
+++ b/dygraph/ppdet/engine/callbacks.py
@@ -79,7 +79,8 @@ class LogPrinter(Callback):
 
     def on_step_end(self, status):
         if ParallelEnv().nranks < 2 or ParallelEnv().local_rank == 0:
-            if self.model.mode == 'train':
+            mode = status['mode']
+            if mode == 'train':
                 epoch_id = status['epoch_id']
                 step_id = status['step_id']
                 steps_per_epoch = status['steps_per_epoch']
@@ -88,8 +89,8 @@ class LogPrinter(Callback):
                 data_time = status['data_time']
 
                 epoches = self.model.cfg.epoch
-                batch_size = self.model.cfg['{}Reader'.format(
-                    self.model.mode.capitalize())]['batch_size']
+                batch_size = self.model.cfg['{}Reader'.format(mode.capitalize(
+                ))]['batch_size']
 
                 logs = training_staus.log()
                 space_fmt = ':' + str(len(str(steps_per_epoch))) + 'd'
@@ -119,14 +120,15 @@ class LogPrinter(Callback):
                         dtime=str(data_time),
                         ips=ips)
                     logger.info(fmt)
-            if self.model.mode == 'eval':
+            if mode == 'eval':
                 step_id = status['step_id']
                 if step_id % 100 == 0:
                     logger.info("Eval iter: {}".format(step_id))
 
     def on_epoch_end(self, status):
         if ParallelEnv().nranks < 2 or ParallelEnv().local_rank == 0:
-            if self.model.mode == 'eval':
+            mode = status['mode']
+            if mode == 'eval':
                 sample_num = status['sample_num']
                 cost_time = status['cost_time']
                 logger.info('Total sample number: {}, averge FPS: {}'.format(
@@ -147,8 +149,11 @@ class Checkpointer(Callback):
             self.ema.update(self.model.model)
 
     def on_epoch_end(self, status):
-        assert self.model.mode == 'train', \
-            "Checkpointer can only be set during training"
+        # Checkpointer only performed during training
+        mode = status['mode']
+        if mode != 'train':
+            return
+
         if ParallelEnv().nranks < 2 or ParallelEnv().local_rank == 0:
             epoch_id = status['epoch_id']
             end_epoch = self.model.cfg.epoch
diff --git a/dygraph/ppdet/engine/env.py b/dygraph/ppdet/engine/env.py
index ad6d8d521c925a64da8c75e4875616184ec912cb..5b59f8acc423c9b7c9ed949ee2f91b31c2f794be 100644
--- a/dygraph/ppdet/engine/env.py
+++ b/dygraph/ppdet/engine/env.py
@@ -35,8 +35,7 @@ def init_parallel_env():
         random.seed(local_seed)
         np.random.seed(local_seed)
 
-    if ParallelEnv().nranks > 1:
-        paddle.distributed.init_parallel_env()
+    paddle.distributed.init_parallel_env()
 
 
 def set_random_seed(seed):
diff --git a/dygraph/ppdet/engine/trainer.py b/dygraph/ppdet/engine/trainer.py
index 62f23038ae17285b4ee42fcbf8be6a3cf401c0c1..32aff4e2522fd9551b7bbd6c2bc339f5acc16330 100644
--- a/dygraph/ppdet/engine/trainer.py
+++ b/dygraph/ppdet/engine/trainer.py
@@ -60,15 +60,19 @@ class Trainer(object):
             slim = create(cfg.slim)
             slim(self.model)
 
-        if ParallelEnv().nranks > 1:
-            self.model = paddle.DataParallel(self.model)
-
         # build data loader
         self.dataset = cfg['{}Dataset'.format(self.mode.capitalize())]
-        # TestDataset build after user set images, skip loader creation here
-        if self.mode != 'test':
+        if self.mode == 'train':
             self.loader = create('{}Reader'.format(self.mode.capitalize()))(
                 self.dataset, cfg.worker_num)
+        # EvalDataset build with BatchSampler to evaluate in single device
+        # TODO: multi-device evaluate
+        if self.mode == 'eval':
+            self._eval_batch_sampler = paddle.io.BatchSampler(
+                self.dataset, batch_size=self.cfg.EvalReader['batch_size'])
+            self.loader = create('{}Reader'.format(self.mode.capitalize()))(
+                self.dataset, cfg.worker_num, self._eval_batch_sampler)
+        # TestDataset build after user set images, skip loader creation here
 
         # build optimizer in train mode
         if self.mode == 'train':
@@ -77,6 +81,9 @@ class Trainer(object):
             self.optimizer = create('OptimizerBuilder')(self.lr,
                                                         self.model.parameters())
 
+        self._nranks = ParallelEnv().nranks
+        self._local_rank = ParallelEnv().local_rank
+
         self.status = {}
 
         self.start_epoch = 0
@@ -103,21 +110,18 @@ class Trainer(object):
             self._compose_callback = None
 
     def _init_metrics(self):
-        if self.mode == 'eval':
-            if self.cfg.metric == 'COCO':
-                self._metrics = [COCOMetric(anno_file=self.dataset.get_anno())]
-            elif self.cfg.metric == 'VOC':
-                self._metrics = [
-                    VOCMetric(
-                        anno_file=self.dataset.get_anno(),
-                        class_num=self.cfg.num_classes,
-                        map_type=self.cfg.map_type)
-                ]
-            else:
-                logger.warn("Metric not support for metric type {}".format(
-                    self.cfg.metric))
-                self._metrics = []
+        if self.cfg.metric == 'COCO':
+            self._metrics = [COCOMetric(anno_file=self.dataset.get_anno())]
+        elif self.cfg.metric == 'VOC':
+            self._metrics = [
+                VOCMetric(
+                    anno_file=self.dataset.get_anno(),
+                    class_num=self.cfg.num_classes,
+                    map_type=self.cfg.map_type)
+            ]
         else:
+            logger.warn("Metric not support for metric type {}".format(
+                self.cfg.metric))
             self._metrics = []
 
     def _reset_metrics(self):
@@ -154,14 +158,16 @@ class Trainer(object):
                 weight_type, weights))
         self._weights_loaded = True
 
-    def train(self):
+    def train(self, validate=False):
         assert self.mode == 'train', "Model not in 'train' mode"
-        self.model.train()
 
         # if no given weights loaded, load backbone pretrain weights as default
         if not self._weights_loaded:
             self.load_weights(self.cfg.pretrain_weights)
 
+        if self._nranks > 1:
+            model = paddle.DataParallel(self.model)
+
         self.status.update({
             'epoch_id': self.start_epoch,
             'step_id': 0,
@@ -175,9 +181,11 @@ class Trainer(object):
         self.status['training_staus'] = stats.TrainingStats(self.cfg.log_iter)
 
         for epoch_id in range(self.start_epoch, self.cfg.epoch):
+            self.status['mode'] = 'train'
             self.status['epoch_id'] = epoch_id
             self._compose_callback.on_epoch_begin(self.status)
             self.loader.dataset.set_epoch(epoch_id)
+            model.train()
             iter_tic = time.time()
             for step_id, data in enumerate(self.loader):
                 self.status['data_time'].update(time.time() - iter_tic)
@@ -185,7 +193,7 @@ class Trainer(object):
                 self._compose_callback.on_step_begin(self.status)
 
                 # model forward
-                outputs = self.model(data)
+                outputs = model(data)
                 loss = outputs['loss']
 
                 # model backward
@@ -196,23 +204,42 @@ class Trainer(object):
                 self.optimizer.clear_grad()
                 self.status['learning_rate'] = curr_lr
 
-                if ParallelEnv().nranks < 2 or ParallelEnv().local_rank == 0:
+                if self._nranks < 2 or self._local_rank == 0:
                     self.status['training_staus'].update(outputs)
 
                 self.status['batch_time'].update(time.time() - iter_tic)
                 self._compose_callback.on_step_end(self.status)
                 iter_tic = time.time()
+
             self._compose_callback.on_epoch_end(self.status)
 
-    def evaluate(self):
+            if validate and (self._nranks < 2 or self._local_rank == 0) \
+                    and (epoch_id % self.cfg.snapshot_epoch == 0 \
+                             or epoch_id == self.end_epoch - 1):
+                if not hasattr(self, '_eval_loader'):
+                    # build evaluation dataset and loader
+                    self._eval_dataset = self.cfg.EvalDataset
+                    self._eval_batch_sampler = \
+                        paddle.io.BatchSampler(
+                            self._eval_dataset,
+                            batch_size=self.cfg.EvalReader['batch_size'])
+                    self._eval_loader = create('EvalReader')(
+                        self._eval_dataset,
+                        self.cfg.worker_num,
+                        batch_sampler=self._eval_batch_sampler)
+                with paddle.no_grad():
+                    self._eval_with_loader(self._eval_loader)
+
+    def _eval_with_loader(self, loader):
         sample_num = 0
         tic = time.time()
         self._compose_callback.on_epoch_begin(self.status)
-        for step_id, data in enumerate(self.loader):
+        self.status['mode'] = 'eval'
+        self.model.eval()
+        for step_id, data in enumerate(loader):
             self.status['step_id'] = step_id
             self._compose_callback.on_step_begin(self.status)
             # forward
-            self.model.eval()
             outs = self.model(data)
 
             # update metrics
@@ -233,6 +260,9 @@ class Trainer(object):
         # reset metric states for metric may performed multiple times
         self._reset_metrics()
 
+    def evaluate(self):
+        self._eval_with_loader(self.loader)
+
     def predict(self, images, draw_threshold=0.5, output_dir='output'):
         self.dataset.set_images(images)
         loader = create('TestReader')(self.dataset, 0)
@@ -242,11 +272,12 @@ class Trainer(object):
         anno_file = self.dataset.get_anno()
         clsid2catid, catid2name = get_categories(self.cfg.metric, anno_file)
 
-        # Run Infer
+        # Run Infer 
+        self.status['mode'] = 'test'
+        self.model.eval()
         for step_id, data in enumerate(loader):
             self.status['step_id'] = step_id
             # forward
-            self.model.eval()
             outs = self.model(data)
             for key in ['im_shape', 'scale_factor', 'im_id']:
                 outs[key] = data[key]
@@ -301,6 +332,8 @@ class Trainer(object):
         if image_shape is None:
             image_shape = [3, None, None]
 
+        self.model.eval()
+
         # Save infer cfg
         _dump_infer_config(self.cfg,
                            os.path.join(save_dir, 'infer_cfg.yml'), image_shape,
diff --git a/dygraph/setup.py b/dygraph/setup.py
index bb60cf0d3275206e3686ea9c340f46e3336929de..2ecdc8c478e0cd148e84b0f37a84ad4547265767 100644
--- a/dygraph/setup.py
+++ b/dygraph/setup.py
@@ -51,6 +51,7 @@ packages = [
     'ppdet.core',
     'ppdet.data',
     'ppdet.engine',
+    'ppdet.metrics',
     'ppdet.modeling',
     'ppdet.model_zoo',
     'ppdet.py_op',
diff --git a/dygraph/tools/eval.py b/dygraph/tools/eval.py
index eb7e60af450cc8271ffb16357db327babfd50953..998710bff9378ea212a431f555edbba3e52c5e89 100755
--- a/dygraph/tools/eval.py
+++ b/dygraph/tools/eval.py
@@ -32,7 +32,7 @@ from paddle.distributed import ParallelEnv
 from ppdet.core.workspace import load_config, merge_config
 from ppdet.utils.check import check_gpu, check_version, check_config
 from ppdet.utils.cli import ArgsParser
-from ppdet.engine import Trainer
+from ppdet.engine import Trainer, init_parallel_env
 
 from ppdet.utils.logger import setup_logger
 logger = setup_logger('eval')
@@ -60,6 +60,9 @@ def parse_args():
 
 
 def run(FLAGS, cfg):
+    # init parallel environment if nranks > 1
+    init_parallel_env()
+
     # build trainer 
     trainer = Trainer(cfg, mode='eval')
 
diff --git a/dygraph/tools/train.py b/dygraph/tools/train.py
index b00b8575cde9746f4ad019fa11131f7dce235111..c6318264c9c06205fd864a5a7ef78d9085dea82d 100755
--- a/dygraph/tools/train.py
+++ b/dygraph/tools/train.py
@@ -84,7 +84,7 @@ def run(FLAGS, cfg):
         trainer.load_weights(cfg.pretrain_weights, FLAGS.weight_type)
 
     # training
-    trainer.train()
+    trainer.train(FLAGS.eval)
 
 
 def main():