The hydro-pneumatic buffer structure of railway vehicle was analyzed, a new type of hydro-pneumatic buffer was designed, and the detailed dynamics mode was established. The static characteristic curve of hydro-pneumatic buffer under different compression rate and dynamic characteristic curve under different impact speed through using the numerical simulation method were calculated. The simulation results show that the biggest impedance force is 1 836.3 kN and buffer capacity reached 221.89 kJ when impact velocity of the new hydro-pneumatic buffer is 5 m/s. New hydro-pneumatic buffer can improve the impact speed of manipulating vehicle, reduce the longitudinal impact and vibration in the train running and satisfy the needs of speed lifting of the trains.