The invention concretely discloses a synthesis method of 2-imidazolidone, which belongs to the technical field of new materials. The synthesis method of the 2-imidazolidone comprises the following steps of S1, mixing: pouring ethidenediamine, urea, dimethylformamide and a solvent into a three-neck flask, and uniformly stirring; S2, heating: after uniformly stirring, heating at the temperature of 110 to 130 DEG C, radiating by adopting a microwave while heating, keeping warm for 2 to 3 hours, then warming to 130 to 150 DEG C, keeping warm for 0.7 to 0.9 hour, and warming to 150 to 160 DEG C again, and keeping warm for 5 to 6 hours; S3, cooling: after heating, cooling, carrying out suction filtration, washing, and removing dimethylformamide; S4, crystallizing. The invention provides the synthesis method of the 2-imidazolidone, which is low in synthesis cost, high in operability, high in raw material utilization efficiency, produces no harmful pollutants, and high in synthesis efficiencyand low in cost.