Aiming at the problem of insufficient sample in air defense missile reliability evaluation test during the performance qualification test, the multistage testing information fusion method was studied in this paper. By analyzing the experimental data of the flight test before the performance qualification test and the missile reliability qualification test stage, the number of missile samples for reliability evaluation was obtained. Combined with the number of samples obtained from the performance qualification test, the confidence limit of missile reliability was evaluated by classical binomial distribution evaluation method. The evaluation results show that the results of multistage testing information fusion are reasonable, and have high application value in the performance qualification test.