This paper studies the dynamic characteristics in the startup processes of liquid oxygen/kerosene space propulsion system.The dynamic mathematical model of the whole propulsion system is set up,and the parameter changing direction of the dynamic process in the liquid oxygen/kerosene liquid rocket engines is studied using Matlab Simulink software.Though we adopt the centralized parameter method to build the engine model,but the inertia, stickiness, compressibility of liquid are taken into account at the same time, so the model can reflect the distributed characteristics of dynamic process of the engines to some extent.