Abstract: A two-speed automatic planetary transmission, including a sun gear, dual planet gears, a planet carrier, a ring gear, a band-type brake ring, and a locking ring. The locking ring is disposed between the outer surface of the ring gear and the inner surface of the annular lug boss, and the inner surface of the locking ring is fixedly connected to the outer surface of the ring gear. Part of the outer surface of the locking ring contacts with the inner surface of the annular lug boss, and another part thereof is sheathed with the band-type brake ring. One end of the band-type brake ring is a fixed end, and is fixedly connected to a transmission shell; and another one is an unfixed end which is connected to a gear shifting actuator.