The invention discloses polyurethane resin, a preparation method thereof and application thereof to a micro cellular elastomer. The polyurethane resin comprises a polyurethane resin component A and a polyurethane resin component B; the polyurethane resin component A and the polyurethane resin component B comprise polyether ester polyol; a ratio of a mole number of active hydrogen in the component A to a mole number of -NCO in the component B is 1:1. The polyether ester polyol is a reaction product of polyether polyol, phthalic anhydride, a double-metal cyanide complex catalyst, epoxypropane, ethylene oxide and a basic catalyst. According to the polyurethane resin and the preparation method and the application thereof, which are disclosed by the invention, under the condition of not adding an open-hole agent and graft polymer polyol, the polyurethane micro cellular elastomer with a low forming density, a high hardness, low shrinkage, high tensile strength and tearing strength, excellent hydrolysis resistance and excellent wear resistance can be prepared, and not only hydrolysis resistance and a forming hardness of the polyurethane micro cellular elastomer are improved, but also the open taphole of the polyurethane micro cellular elastomer is improved, so that cells of the polyurethane micro cellular elastomer are fine and uniform, and shrinkage is low.