The invention discloses a method for protecting a metal layer in a process of thinning a wafer in order to solve the problem that the metal layer of the wafer is easily torn together with a protective film when the protective film is torn in the wafer thinning process in the prior art. The method comprises the following steps of: coating a photoresist layer on the surface of the metal layer of the wafer; carrying out edge adhesive-removing treatment on the metal layer, wherein an edge adhesive-removing width is larger than an edge pressing width; carrying out exposure treatment and development treatment on the metal layer subjected to the edge adhesive-removing treatment; and then etching a part of metal layer in the metal layer of an edge adhesive-removing region to form a protective groove, wherein the part of etched metal layer is the part of metal layer, in which the edge adhesive-removing region and an edge pressing region are not overlapped. By adopting the technical scheme, thepossibility of tearing the metal layer in the wafer thinning process can be reduced to a large extent.