Video monitoring system in substations is an important part of smart grid, which is widely used in operation, management and maintenance of substations. However, there’re some obstacles in communications among devices from different companies. In order to solve these problems, a new test system is designed by a kind of simulation method, which can tests the functions, protocols and capabilities of a real video monitoring system. For the device unqualified, the problem is pointed out by the test system and make it satisfy the needs of video monitoring system. It is showed from the experiments that this test system has a practical application value with its stability, reliability, accuracy and availability.