In order to solve the problem of remote operation and maintenance interoperability test of substation automation based on General Service Protocol (GSP), a conformance test technology of GSP is proposed. A GSP conformance testing system platform is built, which consists of GSP conformance testing tools, remote operation and maintenance master station, remote operation and maintenance objects, protection measurement and control simulation system and other equipment. The affirmative and negative test cases for remote operation and maintenance services are designed, and the service-oriented function interface is provided for custom test case invocation. The conformance testing system can automatically execute the test cases of remote operation and maintenance service, automatically analyze the response messages of the tested objects and output the test results. Conformance testing system realizes full closed-loop in the process of testing, improves the efficiency and quality of testing, and supports the practical application of general service protocol in power system. This work is supported by Science and Technology Project of State Grid Corporation of China (No. SG2020037) “Research and Application of Substation Station-level Localization Communication Protocol”.