The invention discloses a preparation method of ezetimibe and an intermediate thereof. The invention provides a preparation method of ezetimibe intermediate IV, comprising the following steps: in an organic solvent, in the presence of a trialkylchlorosilane, an organic base, a chiral catalyst and lithium diisopropylamide, the ezetimibe The ezetimibe intermediate II and the ezetimibe intermediate III undergo a ring closure reaction to obtain the ezetimibe intermediate IV; R is methyl, ethyl or propyl. The preparation method of the present invention has short route steps, mild reaction conditions, simple post-treatment steps, avoids substrates connected with chiral groups, and the prepared product has high purity, meets the standard of raw materials, high yield, low production cost, and atom utilization High efficiency, suitable for industrial production.