您可以使用:

model=Sequential()
layer=Dense(64,init='glorot_uniform',input_shape=(784,))
layer.trainable=False
model.add(layer)
layer2=Dense(784, activation='sigmoid',init='glorot_uniform')
layer2.trainable=True
model.add(layer2)
model.compile(loss='relu', optimizer=sgd,metrics = ['mae'])