In view of a stage separation system based on high-pressure pneumatic thrusters for low-cost,clean and reusable launch rockets,a reasonable separation sequence was designed.A dynamic model of the separating body was established for different separation stages.A dynamic mathematical model,including gas cylinders,cylinders and pipelines,was established based on the principles of gas dynamics.Finally,a simulation model was built in MATLAB/Simulink,yielding curves of pressure changes in the pneumatic system and changes in the motion parameters of the separating body during the separation process.The influence of parameters such as the diameter of the separation cylinder and the diameter of the gas pipelines on the separation distance was analyzed by simulation.The impact of factors such as residual thrust eccentricity and center of mass deviation on separation was also considered.The Monte Carlo method was used to analyze the relative motion range of the separating body during the separation process.The results show that the established mathematical model can correctly reflect the change of parameters in the separation process,and the relative motion of the separator is within the safe range under the bias interference condition,the feasibility of separation system is verified.