A dual motor power system for a pure electric vehicle and a control method thereof are disclosed, wherein within a range defined between upper and lower torque thresholds for the operations of one of the two motors under current vehicle speed, the torque of this motor is changed stepwise with a certain torque step; the required torque of the other motor is determined based on the torque distribution relation of the first and second motors; and the synchronized efficiency of the power system is determined based on the torques of the first and second motors so that the optimal synchronized efficiency of the power system is ergodically searched out, and the optimal working points of the two motors and the corresponding gear of the second motor are determined then.