The invention discloses a high-purity odorless pirimiphos-methyl preparation method, comprising the following steps: adopting O,O-dimethylthiophosphorylchloride and 2-N,N-diethylamino-4-hydroxy-6-methyl- pyridine as raw materials and toluene, water as solvent and sodium hydroxide as acid-binding agent, adding a hydrolysis inhibitor and reacting in the present of catalyst to obtain the high-purity odorless of pirimiphos-methyl. The reaction equation is as above. In the method of the invention, the hydrolysis inhibitor is added so as to effectively inhibit O,O-dimethylthiophosphorylchloride from performing side reactions such as hydrolysis and the like, increase the conversion rate, reduce impurities and obtain the high-purity odorless pirimiphos-methyl. The toxic impurities are obviously reduced, the product yield and the purity are significantly improved and the industrialized problem of high-quality pirimiphos-methyl is solved.