The invention relates to a manufacture method of a polysilicon emitter of a transistor. The manufacture method comprises that the surface, which comprises an N type collection region, a P type base region, a first oxide layer and a second oxide layer, of a substrate is lithographed and etched to form an emission region window and expose the P type base region whose width is the same with that of the emission region window; un-doped polysilicon is deposited at the surfaces of the first oxide layer and the second oxide layer and in the emission region window so that the un-doped polysilicon completely covers the emission region window; the surface, deposited with the un-doped polysilicon, of the substrate is lithographed and etched to remove un-doped polysilicon beyond the emission region window; doped elements are injected into the un-doped polysilicon in the emission region window by ion implantation technology; and first heat treatment is carried out on the substrate with injected doped elements so that the doped elements in the polysilicon in the emission region window are diffused to the surface layer of the exposed P type base region to form an N type diffusion region.