Abstract: Investigates the realization of DC electrical-closed loading technology and designs the QR512 MT gearbox test bench.Three DC motors were used to build a load simulator in accordance with vehicle's running conditions.SIEMENS S7-315 PLC and 6RA70 DC speed regulator was set up as the controller and driver respectively in the two-level control system.Maximum power of the test bench is 30 kW,dynamic precision of speed control is ±5 r/min and accuracy of torque loading is ±1 N·m.Control accuracy achieved the expected goal and the use of electrical-closed technology greatly reduced the power cost.