diff --git a/examples/model_compress/quantization/observer_quantizer.py b/examples/model_compress/quantization/observer_quantizer.py
index 76a07a00da..cb8c59bd07 100644
--- a/examples/model_compress/quantization/observer_quantizer.py
+++ b/examples/model_compress/quantization/observer_quantizer.py
@@ -41,8 +41,8 @@ def test(model, device, test_loader):
 def calibration(model, device, test_loader):
     model.eval()
     with torch.no_grad():
-        for data, target in test_loader:
-            data, target = data.to(device), target.to(device)
+        for data, _ in test_loader:
+            data = data.to(device)
             model(data)
 
 
diff --git a/nni/algorithms/compression/pytorch/quantization/quantizers.py b/nni/algorithms/compression/pytorch/quantization/quantizers.py
index d3c38eb682..d3b55c64ee 100644
--- a/nni/algorithms/compression/pytorch/quantization/quantizers.py
+++ b/nni/algorithms/compression/pytorch/quantization/quantizers.py
@@ -261,8 +261,6 @@ def compress(self):
                 scale, zero_point = self.calculate_qparams(layer.name, 'weight')
                 module.register_buffer('weight_scale', scale.to(self.device))
                 module.register_buffer('weight_zero_point', zero_point.to(self.device))
-                # todo: recover old_weight to weight, because the compressed
-                # model may be further finetuned.
             if "input" in config.get("quant_types", []):
                 scale, zero_point = self.calculate_qparams(layer.name, 'input')
                 module.register_buffer('input_scale', scale.to(self.device))
@@ -301,11 +299,24 @@ def export_model(self, model_path, calibration_path=None, onnx_path=None, input_
         calibration_config = {}
 
         for name, module in self.bound_model.named_modules():
-            if hasattr(module, 'input_scale') or hasattr(module, 'output_scale'):
+            if hasattr(module, 'weight_scale') or hasattr(module, 'input_scale') or hasattr(module, 'output_scale'):
                 calibration_config[name] = {}
+            if hasattr(module, 'weight_scale'):
+                calibration_config[name]['weight_bit'] = 8
+                val = float(module.weight_scale * module.weight_qmax)
+                calibration_config[name]['tracked_min_weight'] = val
+                calibration_config[name]['tracked_max_weight'] = -val
+                calibration_config[name]['tracked_weight_qmin'] = -127
+                calibration_config[name]['tracked_weight_qmax'] = 127
+                actual_weight = getattr(module, 'old_weight', None)
+                if actual_weight is None:
+                    logger.warning("Can not recover weight for layer %s. "
+                                   "This may lead to a wrong accuracy performance on the backend.", name)
+                delattr(module, 'weight')
+                module.register_parameter('weight', actual_weight)
             # refactor these magic numbers when customizations of dtype and qscheme are ready.
             if hasattr(module, 'input_scale'):
-                calibration_config[name]['weight_bit'] = 8
+                calibration_config[name]['input_bit'] = 8
                 max_input = float(module.input_scale * (module.input_qmax - module.input_zero_point))
                 min_input = float(module.input_scale * (module.input_qmin - module.input_zero_point))
                 calibration_config[name]['tracked_min_input'] = min_input
diff --git a/test/ut/sdk/test_compressor_torch.py b/test/ut/sdk/test_compressor_torch.py
index c78fa982b1..53abdc34ed 100644
--- a/test/ut/sdk/test_compressor_torch.py
+++ b/test/ut/sdk/test_compressor_torch.py
@@ -1,6 +1,7 @@
 # Copyright (c) Microsoft Corporation.
 # Licensed under the MIT license.
 
+import copy
 from unittest import TestCase, main
 import numpy as np
 import torch
@@ -263,6 +264,39 @@ def test_torch_taylorFOweight_pruner_global_sort(self):
         assert all(torch.sum(mask1['weight_mask'], (1, 2, 3)).numpy() == np.array([0., 0., 0, 0., 25.]))
         assert all(torch.sum(mask2['weight_mask'], (1, 2, 3)).numpy() == np.array([125., 125., 125., 125., 125., 125., 125., 0., 0., 0.]))
 
+    def test_torch_observer_quantizer(self):
+        model = TorchModel()
+        # test invalid config
+        # only support 8bit for now
+        config_list = [{
+            'quant_types': ['weight'],
+            'quant_bits': 5,
+            'op_types': ['Conv2d', 'Linear']
+        }]
+        with self.assertRaises(schema.SchemaError):
+            torch_quantizer.ObserverQuantizer(model, config_list)
+
+        # weight will not change for now
+        model = TorchModel().eval()
+        origin_parameters = copy.deepcopy(dict(model.named_parameters()))
+
+        config_list = [{
+            'quant_types': ['weight'],
+            'quant_bits': 8,
+            'op_types': ['Conv2d', 'Linear']
+        }]
+        quantizer = torch_quantizer.ObserverQuantizer(model, config_list)
+        input = torch.randn(1, 1, 28, 28)
+        model(input)
+        quantizer.compress()
+        model_path = "test_model.pth"
+        calibration_path = "test_calibration.pth"
+        calibration_config = quantizer.export_model(model_path, calibration_path)
+        new_parameters = dict(model.named_parameters())
+        self.assertTrue(all(torch.equal(v, new_parameters[k]) for k, v in origin_parameters.items()))
+        self.assertTrue(calibration_config is not None)
+        self.assertTrue(len(calibration_config) == 4)
+
     def test_torch_QAT_quantizer(self):
         model = TorchModel()
         config_list = [{