The cavitation phenomenon at a pressure relief valve and the dynamic coupoing prblem of the hydraulic systim were both investigated by using the computational fluid dynamics (CFD)method.The cavitations in the pressure relief valve and the dynamic movement of the valve were visually simulated by using the FLUENT software.Simulations of the other parts were carried out by a 1-dimensional characteristic method,which was realized by applying the SIMULINK toolbox of MATLAB.The coupling simulation was carried out by employing two parallel-working computers,and the signal data were communicated through TCP/IP.The simulation results show the coupling principle is feasible and effective.