Abstract: To address the high costs, low testing efficiency, and difficulty in reproducing faults associated with whole-machine testing of emergency diesel generator（EDG） speed control systems, a testing platform was designed based on hardware-in-the-loop（HIL） simulation technology. The platform’s functional components primarily include an operator console for human-machine interaction handling model development and test management, a simulator equipped with and running digital models of multiple diesel generator types, performing real-time simulation and signal simulation interaction, with electrical design compatible with multiple speed control system test interfaces and an actuator bench providing electro-hydraulic operating conditions for fuel supply and mechanical support. Additionally, automated test sequences were developed using software like NI TestStand to streamline platform configuration, test execution, and post-processing, enhancing test consistency. Finally, utilizing the established test platform, speed control system testing was completed for two diesel engine types. Under steady-state operating conditions, the rack displacement errors for both engines compared to actual engine data were less than 1%, the steady-state speed fluctuation rates were less than 0.5%, and the instantaneous speed change rates during dynamic testing were less than 9%. Test results met design requirements.