A Aiming at the shortcomings of traditional intelligent substation secondary system test, such as complicated operation and high cost, this paper presents a real-time closed-loop automatic test platform for intelligent substation secondary system. The platform uses dynamic real-time simulation tools to establish the primary system model of substation, and outputs the results to secondary system equipment in accordance with the protocol standard format. It uses hierarchical structure and modularization idea to complete the real-time closed-loop automatic test of secondary equipment of substation, and can automatically generate standardized test results report. The closed-loop automatic test platform designed in this paper can effectively improve the efficiency of the secondary system test of intelligent substation, and can realize standard, real-time and efficient closed-loop test. It plays an important role in the operation and maintenance of the secondary system of intelligent substation.