The invention provides a high-purity 2-pyrimidinethiol preparation method which includes the steps: (1) adding and dissolving reactant 2-chloro-pyrimidine and sulfides into solvents according to the molar ratio of 1:1, adding compound catalysts, controlling reaction temperature to react mixture, and tracking reaction by thin-layer chromatography until the 2-chloro-pyrimidine completely reacts; (2) cooling mixture to reach indoor temperature after reaction, separating out yellow tabular crystals and then performing suction filtration; (3) washing the yellow tabular crystals by water, performing recrystallization on the yellow tabular crystals by the aid of mixed solvents, and filtering and drying mixture to obtain high-purity 2-pyrimidinethiol. Reaction solvents and compound catalysts in the preparation process of the 2-pyrimidinethiol can be repeatedly used, production cost can be reduced, environmental pollution is reduced, continuous production time is saved, and manpower and material resources are saved. The high-purity 2-pyrimidinethiol prepared by the preparation method is low in production cost, good in purity, high in yield, less in environmental pollution and safer to produce, and the yield of the 2-pyrimidinethiol can reach 92.8%.