The present invention relates to a brivaracetam intermediate, a preparation method therefor, and a preparation method for brivaracetam. The steps of the method for preparing brivaracetam described in the present invention are short and the raw materials are cheap, moreover, the method is simple and highly effective without requiring isomer separation by means of column chromatography or asymmetric synthesis, being suitable for industrial large-scale production. In addition, disclosed by the present invention is a compound as shown in formula (II), which may be used for the synthesis of brivaracetam.