Abstract: Electricity enclosed automobile transmission loaded test-bed control system with high rotating speed,large scale torque and high accuracy is designed,which can produce positive torque and negative torque.The test-bed can be used to simulate transmission's practical work condition.Three AC motors are used to process the transmission's driver and loading.SIEMENS S7-315 PLC and 6SE70 inverter are set up as the controller and driver respectively in the two-level control system.It can control the torque of input shaft and output shaft of the tested transmission,and the dynamic precision of speed control is±0.5% and the accuracy of torque loading is±0.5%.When the main driving motor acts as a driver,and the loaded motor acts as a generator,the loaded energy turns into power energy and feedbacks to the system,which not only saves power but also reduces the effect to the outside power network.The results showed that control accuracy achieves the expected goal and the use of electrical-closed system greatly reduces the power cost,which saves about 75% power efficiency.