A unified test platform scheme with flexible structure and configurable function is presented. The primary system model and environment of which equipment runs with different voltage levels are constructed by integrating physical and digital simulation system, etc. through bi-directional interface. The unified system-level test platform for smart substation is also launched by employing configured file and physical device, by which the requirements for closed-loop test can be achieved for relay protection, time synchronization system, network architecture and advanced applications, etc. The platform plays a key role in fault replay and analysis, project debugging, especially in the verification test of secondary device for State Grid Corporation of China. The result shows the better innovation and strong practical.