The invention relates to a preparation method of voriconazole, wherein the preparation method comprises the following specific steps: adding alpha-fluoropropionyl ethyl acetate and a methanol solution of formamidine acetate into a methanol solution of sodium methylate, carrying out cyclization to obtain 6-ethyl-5-fluoropyrimidine-4(3H)-one, chloridizing to obtain 4-chloro-6-ethyl-5-fluoropyrimidine, dissolving 4-chloro-6-ethyl-5-fluoropyrimidine in tetrahydrofuran, dropwise adding into a tetrahydrofuran solution of lithium diisopropylamide, adding a tetrahydrofuran solution of 1-(2,4-difluorophenyl)-2-(1H-1,2,4-triazole-1-yl)ethyl ketone, carrying out a reaction to obtain 3-(4-chloro-5-fluoropyrimidine-6-yl)-2-(2,4-difluorophenyl)-1-(1H-1,2,4-triazole-1-yl)butyl-2-ol, dissolving in ethanol, adding 10% palladium-carbon and sodium acetate, and then splitting to obtain voriconazole. According to the preparation method of voriconazole, the preparation method is simple, and the production cost is low.