The invention relates to a method for processing a dissection retainer ring, which comprises the following steps in processing order: turning machining; dissecting, namely dissecting a retainer ring lathe processing piece to form peripheral non-sealed retainer ring dissected work pieces; adhering, namely adhering dissection ports of the retainer ring processing piece to recover a sealed ring shape; grinding and processing, namely grinding end faces and inside and outside diameter surfaces of the adhered work pieces to finished product dimension; and separating the dissection ports, namely heating the grinded work pieces to melt adhesive, and automatically separating the adhered dissection ports to form a dissection retainer ring finished product. The method performs the dissecting process before the grinding and the processing and then uses the adhesive to adhere and recover the dissection ports, so that the dissection ports do not influence the grinding and the processing of subsequent work pieces, after the work pieces are ground to the finished product dimension, finally the adhesive is melted by heating, and the dissection ports are naturally separated and the form of the grinded work pieces is well kept so as to ensure dimensional precision and shape precision of the finished products and improve the processing precision of the dissection retainer ring.