The invention belongs to the technical field of polyurethane elastomers and preparation thereof and particularly relates to a method for preparing a star-shaped polyurethane elastomer through a simple bulk polymerization method. A simple body one-step method or a bulk prepolymerization method is adopted, occurrence of cross-linking reaction is avoided by regulating the proportion and molecular weight of polyols, efficient controllable synthesis of the thermoplastic star-shaped polyurethane is implemented, and thus the star-shaped polyurethane elastomer with the improved mechanical properties is obtained. Due to the adoption of the bulk prepolymerization method, the star-shaped polyurethane complex in structure can be obtained by two steps at most, raw materials are easy to obtain and cheap, requirements for a device are low, because the star-shaped polyurethane elastomer not only is simple to operate, short in preparation cycle and high in efficiency, but also can reduce device investment, and the production cost is reduced. The process for preparing the star-shaped polyurethane elastomer belongs to the bulk polymerization method, a shortcoming of preparation through a solvent in the prior art is overcome, no catalyst is used, and thus the production process is green and environmentally friendly and favorable for popularization and application.