Abstract: A motion detection circuit and a motion detection method are provided. The motion detection circuit includes a motion vector (MV) filtering unit and a MV decision unit. According to a relationship between a MV of a current macro-block (MB) and MVs of spatial neighboring MBs, or according to a relationship between the MV of the current MB and the MV of temporal neighboring MB, the MV filtering unit determines whether to filter the MV of the current MB for obtaining a first filtered information of the current MB. The MV decision unit receives the first filtered information, and determines whether the current MB is a motion MB according to the first filtered information.