The invention discloses a method for preparing ezetimibe. The method comprises the following steps: adding dichloromethane into a reactor, adding ezetimibe-ketone into the reactor in the stirring process, and adding (R)-2-methyl-CBS-oxazaborolidine; reacting in the presence of a catalyst, transferring into a toluene solution, and performing mixing and stirring treatment through a stirring rod; slowly adding a dichloromethane solution in the stirring process, adding a mixed solution again, adding strong base into the solution for washing, drying by using anhydrous sodium sulfate, filtering and crystallizing, filtering, detecting the acid-base property of the crystal by utilizing pH paper until the solution is neutral, drying, thereby obtaining the ezetimibe. The reaction yield is high, the product purity is high, the cost is low, use of toxic reagents is avoided, the environmental influence is obviously reduced, and the method is suitable for large-scale industrial production.