Embodiments of the invention provide a fabricating method a thin film transistor, a thin film transistor and a display panel, so as to improve carrier mobility in the polycrystalline silicon. The fabricating method a thin film transistor comprises following M1, depositing an inducing layer on a substrate; M2, etching a recess in the inducing layer by an etching process, the recess having an edge with a prescribed shape; M3, depositing an amorphous silicon layer in the recess having an edge with a prescribed shape, and inducing the amorphous silicon layer to form a polycrystalline silicon layer by crystallization method, polycrystalline silicon grains in the polycrystalline silicon layer arranging in a direction vertical to the edge of the recess by the limitation of the edge of the recess, and the polycrystalline silicone layer and the inducing layer together forming a semiconductor layer; and M4, forming a gate insulating layer, a gate, a passivation layer and a source and a drain connecting with the semiconductor layer sequentially on the semiconductor layer.