A reliability model was presented when test data were used to assess the reliability of system. Considering the property of ballistic discrimination fuze, not only the experimental data of shooting range, but also the data of simulated test should be used. The pattern building method of the ballistic discrimination fuze reliability was investigated, which is used to evaluate reliability of system. The research was carried out based on the analysis of advantages and disadvantages between the structural model building method and the functional model building method. The method that structure and function were “converted” was established, and the reasonable establishment of the ballistic discrimination fuze reliability model provides a reference for the follow-up research.