The invention relates to a polishing pad, a polyurethane polishing layer and a preparation method thereof, and belongs to the field of a polishing technology for chemical mechanical planarization processing. The polyurethane polishing layer with the coefficient of thermal expansion being 70 to 200ppm/DEG C contains a reaction product generated by multi-component reaction. The multiple components comprise an isocyanate end-capped prepolymer, a hollow microporous polymer and a curing agent composition. The curing agent composition comprises 5-55 weight percent of aliphatic diamine composition, 0-8 weight percent of polyamine composition, and 40-90 weight percent of aromatic bifunctional composition. The polyurethane polishing layer has the density being 0.6- 1.1g/cm<3>, the shore harness being 45-70 D, and the elongation at break being 50-450 percent. A preparation process of the polyurethane polishing layer is simple, low in cost and small in energy consumption, and the polyurethane polishing layer prepared through the process has the advantages of high hydrolytic stability, uniform density, stable removal rate and the like.