We have studied the fine procedure and characters of the microstructures for the a-Si:H and a-Si films, which have been changed from amorphous phase to microcrystalline phase, by means of Rigaku 3015 type X-ray diffraction spectroscope and high resolution electronic microscopy (HREM). This research provides some intuitive information for the transformation process, in which amorphous silicon filims change over from amorphous phase to micro-crystalline phase, and further deepens the understanding for the microstructures of amorphous silicon films.