The amorphous silicon TFT (α-Si thin film transistor) were fabricated in a new structure, in which the ohmic contact layer (n+ layer) and the nitride silicon insulating layer for grid (G-SiNx) were stratified. Various factors which affect the electron mobility of α-Si TFT are studied using orthogonal test. With the increase in the number of n+ layer, the electronic mobility also rises. Besides, G-SiNx should be stratified into a rapid deposition film (GH) and a low-speed growing film (GL). The thickness of GL should be increased, with the thickness of GH reduced accordingly to achieve the electron mobility gradually increasing. Finally, based on the experimental results in the orthogonal combination experiments, the α-Si TFT mobility can stably reach 0.66 cm2/V·s, much higher than the traditional volume production data (0.29 cm2/V·s).