Abstract: The stability of the electro-hydraulic variable valve hydraulic system is of great significance to the combustion and emissions of the engine. Therefore, in view of a certain type electro-hydraulic variable valve system developed dependently for marine diesel engine, this paper established the evaluation system of pressure fluctuation, and analyzed the influence of coupling of oil supply pressure P₀ (10 to 13 MPa) and electromagnetic valve opening phase β (317~322 °CA) on pressure fluctuations through the experiment and simulation. The characteristic value P_a–e and characteristic phase β_a–e at the inflection point of the instantaneous pressure change curve of the hydraulic oil circuit pressure curve in front of the solenoid valve are affected by the supply pressure and the opening phase of the solenoid valve. The results show that the amplitudes of the characteristic parameters of pressure fluctuation, P_a, P_c and P_e, are not affected by the opening phase of the solenoid valve. The amplitudes of P_b and P_d increase with the delay of the opening phase of the solenoid valve. With the increasing of pressure fluctuation characteristic parameters P_a, P_c and P_e increases with the increase of oil supply pressure, and the decrease of pressure fluctuation characteristic parameters P_b and P_d increases with the increase of oil supply pressure. The interval difference between characteristic phase β_a–e is almost independent of the oil supply pressure and almost identical to the interval difference between the opening phases of the solenoid valve.