A transmission mechanism of a hub drive automatic transmission motor of an electric vehicle is composed of a hub, an upper end cover, a lower end cover, the motor, an automatic transmission, a planetary gear speed reducing mechanism, a spindle and the like. The transmission mechanism is characterized in that the automatic transmission is provided with a sun gear fixing plate, a driving disc, a cover casing, a location plate and a planetary gear reducer. Magnetic steel is arranged outside the cover casing, a stator is arranged outside the magnetic steel, the stator is fixed on a motor casing, the cover casing is connected with the location plate along an opening, and the spindle is fixedly connected with the motor casing and a planetary carrier of the planetary gear speed reducing mechanism through the center of the automatic transmission and extends to the outside of the upper cover and the lower cover to be fixedly connected with a vehicle frame. The motor casing and the planetary carrier of the planetary gear speed reducing mechanism are matched with an upper end cover bearing inner hole and a lower end cover bearing inner hole, a sun gear is matched with the sun gear fixing plate, a shoe block is connected with a pull spring, a diving disc is connected with a driving gear through a driving disc spline, the driving gear drives a planetary gear which drives a gear ring, the gear ring is fixedly connected with the upper end cover or the hub, and the upper end cover and the lower end cover are connected with the hub to form the transmission mechanism of the hub drive automatic transmission motor of the electric vehicle.