The invention relates to a method for preparing a polyurethane polishing disc, in particular to a proportioning and a preparing process of the polyurethane polishing disc. The method comprises the following steps: taking toluene diisocynate, polyether polyol, a chain extender, a cross-linking agent, a copolymer of polysiloxane and polyalkoxy-ether and cerium oxide as raw materials based on the weight ratio of 100:200-240:45-60:16-25:1.5-2.5:90-110; and pre-polymerizing the toluene diisocynate and the polyether polyol to form component A, mixing the chain extender, the cross-linking agent, the copolymer of polysiloxane and polyalkoxy-ether and the cerium oxide to form component B, adding the component A and the component B to a vacuum closed mixing vessel to mix quickly for 5-15 seconds, infusing the components into a die, cooling and curing into polyurethane blank, and then cutting the blank into slices to finally obtain the polyurethane polishing disc. The polyurethane polishing disc obtained by the method of the invention has good elasticity and good microcellular structure and can be used in high-precision grinding and polishing process of various lenses, glasses, prisms, mirror surfaces, optical parts and other glass products. The method of the invention has the advantages of good wear resistance, high polishing efficiency, high polishing precision, high cutting rate, no passivation, simple and convenient operation, low cost and the like.