The invention discloses a dihydrocholesterol preparation method. Cholesterin and hydrogen serve as the raw materials; the raw materials are subjected to a hydrogenation reaction in the presence of raney nickel or palladium charcoal or platinum carbon catalyst at the temperature of 30 to 85 DEG C in a low-carbon alcohol solvent with 1-4 carbon atoms; after the reaction, dihydrocholesterol is obtained through separation and drying; and the yield is more than or equal to 95 percent and the purity is more than or equal to 96 percent. During the dihydrocholesterol preparation, the dihydrocholesterol serves as the raw material; the raw material is subjected to oxidation reaction for at least 2 hours with oxidizers, such as potassium permanganate or potassium dichromate or a Jone reagent and thelike, in a solvent, such as tert-butyl alcohol or water or acetone and the like, at the temperature of more than or equal to 25 DEG C until the boiling point of the solvent; after the reaction, the cholestanone is obtained through separation and drying; and the yield is more than or equal to 92 percent and the purity is more than or equal to 97 percent. The preparation method has mild hydrogenation and oxidation conditions, and simple process, is smooth in reaction, stable in quality, and convenient to operate, and is applicable to scale production. The preparation method also has the advantages of small catalyst amount, regeneration, solvent recovery and no three-waste discharge.