The invention relates to a preparation method of 4-methylthiazol. The invention aims at solving the problem that in the existing method for preparing the methylthiazol, the reaction route is long, the reaction is complicated and not easy to control, the production cost of the used catalyst is high and the yield is high. The preparation method comprises the following steps of A, mixing formamide, anhydrous glycol dimethyl ether and phosphorus pentasulfide, heating the mixture to be reacted at the temperature of 45 to 50 DEG C, and filtering the mixture to obtain thioformamide; B, adding chloroacetone into the thioformamide to be reacted at the temperature of 50 to 60 DEG C, adjusting the pH value to 6 to 7, and cooling, filtering, washing and dehydrating the mixture to obtain the 4-methylthiazol. Raw materials are cheap and easy to obtain, the reaction condition is moderate, the synthesis step is simple, no catalyst is used, no pollution exists, the yield is high, operation is simple and convenient, and the solvent can be recycled. The preparation method is applied to the technical field of chemical industry.