The invention provides a process method for eliminating the undercut defect of a metal silicide blocking layer subjected to wet etching, which is used to eliminate the undercut of the blocking layer.The method comprises the following steps of polysilicon lithography; polysilicon reoxidation; photolithography in a well region; ion injection in a well region; oxide layer etching; photolithography in another well region; ion injection in another well region; oxide layer etching; overall photolithography; and overall etching. The method has the advantageous effect that the multiple-etching methodis used to reduce the load effect in the wet processing, and the undercut problem is effectively solved in the wet etching process. The method is to use a high-pressure shallow doping mask, leading to no increase in cost.