Abstract: Based on the dynamic adjustment of regulator in pressuring and working processes of engine,a dynamic mathematical model of converse and unloading regulator that was usually applied in Liquid Rocket Engine was built.The numerical simulation adopted four-step Runge-Kutta method.The dynamic characteristics of regulator were analyzed in starting boosting pressure.Calculated exit prssure transients of the reduces are in good agreement with those measured in the experimental diagnostics for various inlet pressures.The results show that the analytical model is correct and the simulation method is in accordance with the precision reguirements.The study and its conclusions are useful for the design of congener regulators and the system analyses.