diff --git a/fastNLP/core/optimizer.py b/fastNLP/core/optimizer.py
index ff2ee40e..72737b81 100644
--- a/fastNLP/core/optimizer.py
+++ b/fastNLP/core/optimizer.py
@@ -2,61 +2,28 @@ import torch
 
 
 class Optimizer(object):
-    """Wrapper of optimizer from framework
+    def __init__(self, model_params, **kwargs):
+        if model_params is not None and not isinstance(model_params, torch.Tensor):
+            raise RuntimeError("model parameters should be torch.Tensor, rather than {}".format(type(model_params)))
+        self.model_params = model_params
+        self.settings = kwargs
 
-            1. Adam: lr (float), weight_decay (float)
-            2. AdaGrad
-            3. RMSProp
-            4. SGD: lr (float), momentum (float)
 
-    """
+class SGD(Optimizer):
+    def __init__(self, model_params=None, lr=0.001, momentum=0.9):
+        super(SGD, self).__init__(model_params, lr=lr, momentum=momentum)
 
-    def __init__(self, optimizer_name, **kwargs):
-        """
-        :param optimizer_name: str, the name of the optimizer
-        :param kwargs: the arguments
-
-        """
-        self.optim_name = optimizer_name
-        self.kwargs = kwargs
-
-    @property
-    def name(self):
-        """The name of the optimizer.
-
-        :return: str
-        """
-        return self.optim_name
+    def construct_from_pytorch(self, model_params):
+        if self.model_params is None:
+            self.model_params = model_params
+        return torch.optim.SGD(self.model_params, **self.settings)
 
-    @property
-    def params(self):
-        """The arguments used to create the optimizer.
 
-        :return: dict of (str, *)
-        """
-        return self.kwargs
+class Adam(Optimizer):
+    def __init__(self, model_params=None, lr=0.001, weight_decay=0.8):
+        super(Adam, self).__init__(model_params, lr=lr, weight_decay=weight_decay)
 
     def construct_from_pytorch(self, model_params):
-        """Construct a optimizer from framework over given model parameters."""
-
-        if self.optim_name in ["SGD", "sgd"]:
-            if "lr" in self.kwargs:
-                if "momentum" not in self.kwargs:
-                    self.kwargs["momentum"] = 0
-                optimizer = torch.optim.SGD(model_params, lr=self.kwargs["lr"], momentum=self.kwargs["momentum"])
-            else:
-                raise ValueError("requires learning rate for SGD optimizer")
-
-        elif self.optim_name in ["adam", "Adam"]:
-            if "lr" in self.kwargs:
-                if "weight_decay" not in self.kwargs:
-                    self.kwargs["weight_decay"] = 0
-                optimizer = torch.optim.Adam(model_params, lr=self.kwargs["lr"],
-                                             weight_decay=self.kwargs["weight_decay"])
-            else:
-                raise ValueError("requires learning rate for Adam optimizer")
-
-        else:
-            raise NotImplementedError
-
-        return optimizer
+        if self.model_params is None:
+            self.model_params = model_params
+        return torch.optim.Adam(self.model_params, **self.settings)
diff --git a/fastNLP/core/trainer.py b/fastNLP/core/trainer.py
index d4bedb6f..fb9ba25b 100644
--- a/fastNLP/core/trainer.py
+++ b/fastNLP/core/trainer.py
@@ -12,7 +12,7 @@ from fastNLP.core.batch import Batch
 from fastNLP.core.dataset import DataSet
 from fastNLP.core.losses import _prepare_losser
 from fastNLP.core.metrics import _prepare_metrics
-from fastNLP.core.optimizer import Optimizer
+from fastNLP.core.optimizer import Adam
 from fastNLP.core.sampler import RandomSampler
 from fastNLP.core.sampler import SequentialSampler
 from fastNLP.core.tester import Tester
@@ -31,7 +31,7 @@ class Trainer(object):
     def __init__(self, train_data, model, losser=None, metrics=None, n_epochs=3, batch_size=32, print_every=-1,
                  validate_every=-1,
                  dev_data=None, use_cuda=False, save_path="./save",
-                 optimizer=Optimizer("Adam", lr=0.01, weight_decay=0), need_check_code=True,
+                 optimizer=Adam(lr=0.01, weight_decay=0), need_check_code=True,
                  metric_key=None,
                  **kwargs):
         super(Trainer, self).__init__()
@@ -178,7 +178,7 @@ class Trainer(object):
         for name, num in res.items():
             self._summary_writer.add_scalar("valid_{}".format(name), num, global_step=self.step)
         if self.save_path is not None and self._better_eval_result(res):
-            self.save_model(self.model,
+            self._save_model(self.model,
                             "best_" + "_".join([self.model.__class__.__name__, self.metric_key, self.start_time]))
 
     def _mode(self, model, is_test=False):
@@ -225,7 +225,7 @@ class Trainer(object):
         """
         return self.losser(predict, truth)
 
-    def save_model(self, model, model_name, only_param=False):
+    def _save_model(self, model, model_name, only_param=False):
         model_name = os.path.join(self.save_path, model_name)
         if only_param:
             torch.save(model.state_dict(), model_name)
diff --git a/test/core/test_optimizer.py b/test/core/test_optimizer.py
new file mode 100644
index 00000000..26e47d43
--- /dev/null
+++ b/test/core/test_optimizer.py
@@ -0,0 +1,21 @@
+import unittest
+
+import torch
+
+from fastNLP.core.optimizer import SGD
+
+
+class TestOptim(unittest.TestCase):
+    def test_case(self):
+        optim = SGD(torch.LongTensor(10))
+        print(optim.__dict__)
+
+        optim_2 = SGD(lr=0.001)
+        print(optim_2.__dict__)
+
+        optim_2 = SGD(lr=0.002, momentum=0.989)
+        print(optim_2.__dict__)
+
+    def test_case_2(self):
+        with self.assertRaises(RuntimeError):
+            _ = SGD(0.001)
diff --git a/test/core/test_trainer.py b/test/core/test_trainer.py
index 7c0a1a9d..08df6a49 100644
--- a/test/core/test_trainer.py
+++ b/test/core/test_trainer.py
@@ -4,3 +4,4 @@ import unittest
 class TestTrainer(unittest.TestCase):
     def test_case_1(self):
         pass
+