The invention discloses an outdoor pole-mounted vacuum circuit breaker which comprises a base and three post terminals on the base. The base is internally equipped with a closing power mechanism and an opening power mechanism, and is further internally equipped with a transmission mechanism for transmitting power. Each post terminal is internally equipped with an opening-closing mechanism. A bracket is arranged inside the base. A lower mounting plate and a side mounting plate are arranged on the bracket. A lower positioning component and a side positioning component are respectively arranged on the lower mounting plate and the side mounting plate. The lower positioning component includes a lower positioning main plate and a lower positioning auxiliary plate. Main support plates fixedly connected with the lower positioning main plate are respectively arranged on the side faces of the two ends of the lower positioning main plate. Main plate bolts connecting the lower positioning main plate and the lower mounting plate are arranged between the lower positioning main plate and the lower mounting plate. Auxiliary support plates fixedly connected with the lower positioning auxiliary plate are respectively arranged on the side faces of the two ends of the lower positioning auxiliary plate. Auxiliary bolts connecting the lower positioning auxiliary plate and the lower positioning main plate are arranged between the lower positioning auxiliary plate and the lower positioning main plate. The lower positioning main plate, the lower positioning auxiliary plate and the two auxiliary support plates form a horizontal track hole.