The present invention relates to a reaction system for preparing polyurethane microcellular foam, a polyurethane microcellular foam and the use thereof. The reaction system for preparing polyurethane microcellular foam comprises isocyanate prepolymer, polyols, catalysts and chain extenders. The isocyanate prepolymer is a reaction product of polyisocyanates and polyester polyols, wherein the polyester polyols comprise 10-60 wt. % succinic acid units, based on 100 wt. % of the polyester polyols, the NCO content of the isocyanate prepolymer is 13-30 wt. %, based on 100 wt. % of isocyanate prepolymer. By using the reaction components provided in the present invention, the demould time for preparing the polyurethane microcellular foam can be reduced. The obtained polyurethane microcellular foam, which possesses good physical and mechanical properties, is particularly suitable to prepare shoes.