A method for fabricating a Polysilicon Thin-Film Transistor is provided. The method includes forming a polysilicon active layer, forming a first gate insulation layer and a first gate electrode sequentially on the active layer, conducting a first ion implantation process on the active layer by using the first gate electrode as a mask to form two doped regions at ends of the active layer, forming a second gate insulation layer and a second gate electrode sequentially on the first gate insulation layer and the first gate electrode, and conducting a second ion implantation process on the active layer by using the second gate electrode as another mask to form two source/drain implantation regions at two outer sides of the doped regions of the active layer. Accordingly, impurity concentration of the two doped regions is smaller than that of the two source/drain implantation regions.