The hydro-pneumatic (HPS) system is a key component and important support for aviation aircraft, engineering machinery, special vehicles and other mechanical equipment, which plays a vital role to ensure the stability and operational efficiency of the equipment. To accurately and reliably describe the dynamic characteristics of the HPS system, a nonlinear mathematical model integrating fluid mechanics-related theories and the ideal gas state equation was established. The stiffness and damping characteristics of the HPS system were subjected to dynamic simulation analysis, and a bench performance test was designed for verification, the dynamic response characteristics of the swing-cylinder HPS under sinusoidal excitation were tested. The results show that the experimental data of the HPS are basically consistent with the simulation results, which proves the accuracy of the established nonlinear mathematical model for the HPS, and the model can be used to simulate the dynamic characteristics of HPS. The findings could provide an important reference for the optimized design, performance evaluation, and condition monitoring of HPS system.