Aimed at the characteristics of a small sample of life data of a domestic NC system, the fitting models of test end time, average end ratio, average failure number, number of NC systems and average failure rate were obtained by using multiple linear regression theory. In order to use the life data of other types of systems, the selfhelp method was adopted to determine the prior information distribution parameters, and the results obtained by using the inverse transformation method and the screening sampling method were compared to determine the superparameters, so as to ensure the effectiveness of the reliability evaluation of the NC system