In this paper, a set of electromagnetic valve current characteristic test system is designed to improve the reliability of the trip solenoid valve in the field steam turbine system of nuclear power plant. The test system starts from the field requirements, working principle of solenoid valve, software control and other aspects to complete the pressure suppression function of the hydraulic test system and the functions of data acquisition, storage, display, playback and so on. The test system is composed of a hydraulic system and an electrical control system. The system verifies the reliability of the tested object by detecting the important parameters of the solenoid valve, calibrating the current characteristic points, calculating the characteristic parameters, and judging whether the test is qualified. The test results show that the system has been successfully applied in nuclear power field, meets the needs of the site, and works well.