Abstract: How to acquire proper prior distribution is a key problem in complex system Bayesian reliability evaluation.In this paper,the application of similar system reliability information to system reliability evaluation is studied.By weighting factor,similar system's information was converted to the prior information of a new system.The reliability test data based on Weibull and exponential distribution model is analysied,and reliability evaluation formula is presented.Finally an example is given to show this method is simple in computation and usable in application.