Abstract
A preparation method of a polyurethane resin including the following steps is provided. A liquid polyamine compound is placed in a continuous reaction system, and the liquid polyamine compound is circulated in the continuous reaction system. A solid bis(cyclic carbonate) and a solid catalyst are placed in the continuous reaction system to mix the solid bis(cyclic carbonate), solid catalyst, and liquid polyamine compound to form a heterogeneous mixture. The heterogeneous mixture is heated in the continuous reaction system in a microwave manner, such that the heterogeneous mixture reacts to form a polyurethane resin.