The present invention is a three speed output planetary gear reducer that relates to a speed reducer and comprises a chassis component, a stator component I, a stator component II, a rotor component I, a rotor component II, a controller I, a controller II, a double planetary gear reduction component, and an output gear component. The gear reducer has three output shafts, the output shaft I is theoutput gear driven by a planetary support II of a planetary gear member II. During operation of the reducer, the output rotational speed of the planetary support II is related to the rotational speeddifference of two electric motors which can always be at a high speed operating condition, the rotational direction of the planetary support II of the reducer can be changed under the condition that the rotational direction of the two electric motors is not changed, a loading device is driven to realize frequent operations of acceleration, deceleration and stopping, and even the rotational direction of the loading device is frequently changed. The reducer can ensure that the motors operate at a high-efficiency operating state.