Abstract: An automatic transmission for an electric vehicle hub includes an external motor rotor fixedly connected with a motor shaft; a sun gear; at least three primary planet gears which are engaged with the sun gear; and at least three secondary planet gears coaxially fixed with the primary planet gears. The primary and the secondary planet gears are engaged with a primary and a secondary internal gears, and the secondary internal gear has a diameter greater than that of the primary internal gear. The rotating disk is arranged between the primary internal gear and the secondary internal gear, and a hub is fixed to exterior of the rotating disk. The automatic transmission further includes a clutch device, making the rotating disk and the primary internal gear contact with each other for a transmission of slower rpm, and when the rpm reaches critical, at a high-speed rotation.