The invention relates to a wafer thinning method which comprises the following steps of: providing a substrate and a wafer, wherein the wafer is provided with a first surface, a second surface opposite to the first surface and a lateral surface for connecting the first surface with the second surface and the lateral surface is of an arc shape; cutting part of lateral surface with thickness in the direction from the first surface to the second surface, so that the part of lateral surface with thickness is of a vertical shape; fixing the first surface of the wafer with the substrate; thinning the second surface of the wafer. According to the wafer thinning method, only part of the arc lateral surface of the wafer is cut; the cut part is of a vertical shape; the vertical lateral surface is connected with the first surface of the wafer, then the first surface of the wafer is fixed with the substrate together and part of the arc lateral surface is cut, so that the cut thickness of each wafer is reduced, and further, the cutting efficiency is improved, the processing efficiency is improved, loss of a cutting tool in each cutting process is reduced, the use frequency of the cutting tool is increased and the service life of the cutting tool is prolonged.