With the development of new energy automotive industry, the reliability of vehicle battery management system (BMS) is one of the key factors to ensure electric cars work reliable. We develop a BMS testing system which provides convenient testing method for testing and fault diagnosis of BMS. It achieves the functions of monitoring and testing the distributed BMS. This test system achieves the testing and monitoring between the upper machine and BMS by CAN communication to exchange the information. This paper focuses on the implementation method of CAN data communication between the upper machine and the BMS controller.