The load sensitive system of constant displacement pump is prone to pressure shock when unloading rapidly, which is harmful to the reliability and life of the system. As the three-way pressure compensation valve is the key pressure regulating element in the load sensitive system of constant displacement pump, the three-way pressure compensation valve was studied to find the suppression scheme of the system unloading pressure shock. Firstly, the power bond graph model of the system was built, and the state equation of the system were deduced. Then the dynamic simulation model of Matlab was established according to the state equation. After that, the correctness of the simulation model was verified by the simulation and test analysis of unloading pressure shock. The influences of the damping of pressure chamber, diameter of valve core, damping of Ls chamber and the cone angle of valve port on unloading pressure shock were analyzed by using the simulation model. Finally, based on the structure optimization of three-way pressure compensation valve, a new type of three-way pressure compensation valve with double valve ports was proposed, and it was verified that the valve could effectively suppress the unloading pressure shock. The simulation and experimental results showed that the new valve could effectively suppress the unloading pressure shock, and the optimized system reduced the unloading pressure shock by 89% compared with the original system, at the same time, it also reduced the unloading pressure by 20%, further realizing the energy saving.