The present application relates to a method for preparing a cholic acid compound. Specifically, the method prepares a compound as shown in formula I, including subjecting a compound of formula 2 to an oxidization reaction to obtain a compound of formula 3; attaching a trimethylsilyl group to the compound of formula 3 to obtain a compound of formula 4; reacting the compound of formula 4 with acetaldehyde to obtain a compound of formula 5; subjecting the compound of formula 5 to a catalytic hydrogenation reaction to obtain a compound of formula 6; and converting a cyano group of the compound of formula 6 to a carboxyl group to give the compound of formula I.