Abstract: System pressure valve is very important for the performance of AT. The new system pressure valve in FWD 8AT is designed combined with the calculation model and dynamic simulation model. The dimension structure of valves is designed by theoretical calculation. The dynamic simulation model of hydraulic system of FWD 8AT is established. Simulation results and theoretical results are compared to confirm the simulation model. Based on the confirmed simulation model, the simulation results of pressure and flow of system pressure valve are analyzed. The results show that the dynamic simulation method would be very helpful during the course of designing and analyzing the performance of system pressure valve and further optimization design. The theoretical method and dynamic simulation model will be feasible for the real industrial applications.