The performance of HPS directly influences the comfort of vehicle, dynamic load of wheels and travel distance of suspension. In order to describe and evaluate the performance of HPS, the structure and working principle of main parts of the HPS are introduced and analyzed in this paper firstly. Then the physical model is founded by analyzing and simplifying the structure of HPS. According to the physical model, non-linear mathematical models of HPS with dual gas-accumulators are built up and a special program is composed. The results of computer simulation are carried out through the program. Then a testing rig for HPS is designed and manufactured after rebuilding cylinders and abundant experiments are performed on the testing rig. Comparisons are drawn between the results of simulation and testing, which manifest the mathematical model of HPS built in the thesis is feasible.