Abstract: A pump fed Liquid Rocket Engine (LRE) is researched.Based on the actual variation range of the internal interfering factors,the method of drawing random sample,the estimate method of the probability density parameters and the method of Pearson's chi square test are employed.On the various conditions that each internal interfering factor obeys the normal distribution,Weibull distribution and uniform distribution respectively,a nonlinear mathematical model of static characteristics of LRE is employed to simulate stochastically the effects of the internal interfering factors on the engine performance,and to obtain the statistical distribution laws of the engine performance parameters.