An ion implantation method is provided. The method, before ion implanting, is to rotate the substrate by an angle and shift the scan path of the ion beam with an interlace pitch in the direction perpendicular to the scan direction and on the plane of the substrate. Therefore a plurality of interlaced and not overlapped ion implantation scan lines are formed on the surface of the substrate, so the method can enhance the uniformity of the dose of the ion implantation in the substrate.