Aiming at the test platform of variable valve mechanism for a marine diesel engine, the electronic control system of test platform was designed. The design was divided into four parts including control unit, upper computer, sensor and actuator. According to the system requirements, the suitable sensors and actuators were selected and the hardware circuit and control method of electronic control system were designed and developed. The results show that the electronic control system can receive the sensor signal and output the control signal to drive the solenoid valve to change the valve timing and lift. In the cam rated speed range of 186-425 r/min, the variable range of valve close timing is 0°-70°CA and the maximum additional lift can reach 5 mm. At cams maximum speed of 550 r/min, the additional lift can also reach 5 mm, which can meet the test requirements.