Solved by jerryzh168 in post #2 
              
              
                This is because there is duplicated QuantStub placed in the model, I think forward should be: 
def forward(self, x):
    # manually specify where tensors will be converted from floating
    # point to quantized in the quantized model
    x = self.quant(x)
    x = self.features(x)
    x = self.avgpoo…