The torque distribution of the front and rear four-wheel drive system motors of pure electric vehicles generally adopts a fixed ratio. This paper dynamically adjusts the torque distribution ratio of the front and rear motors according to the driver's torque request and the current vehicle speed. The efficiency analysis model is built with simulink, and the simulink model is called with ISIGHT to obtain the most efficient torque distribution ratio based on vehicle speed and torque request. The whole vehicle simulation model is built by Modelica to simulate and analyze the efficiency of the motor system under three typical operating conditions of NEDC, WLTC, and FTP75, and compare the motors in the three drive modes of single-motor drive, fixed torque distribution ratio, and dynamic adjustment of torque distribution ratio. System efficiency found: dynamic adjustment of the torque output ratio can greatly improve the efficiency of the motor system under FTP75 working conditions. In the power system used in this paper, the single motor drive efficiency is the best under the condition of a small torque request at the same vehicle speed. With the increase of the torque request, the motor system reaches its best efficiency when the torque output ratio of the front motor is around 0.3.