Abstract: An advanced reliability growth model,exponential model,was presented to estimate the model parameters for multi-systems,which was synchronously tested,synchronously censored,and synchronously improved.In the presented method,the data during the reliability growth process were taken into consideration sufficiently,including the failure numbers,safety numbers and failure times at each censored time.If the multi-systems were synchronously improved many times,and the reliability growth of each system fitted AMSAA model,the failure time of each system could be considered rationally as an exponential distribution between two adjoining censored times.The nonparametric method was employed to obtain the reliability at each censored time of the synchronous multi-systems.The point estimations of the model parameters,a and b,were given by the least square method.The confidence interval for the parameter b was given as well.An engineering illustration was used to compare the result of the presented method with those of the available models.The result shows that the presented exponential growth model fits AMSAA-BISE model rather well,and two models are suitable to estimate the reliability growth for the synchronously developed multi-systems.