The fault tree analysis was utilized to analyze the reliability of a new separate flight data recording and tracking system. The fault tree with system failure as the top event was built, and the probability of minimal cut set, the occurrence probability of top event and the sequence of fault probability of each subsystem were obtained. By comparing the criticality importance of each subsystem, the most vulnerable part of the separate flight data recording and tracking system was located, and then the system was optimized. The results show that the soft-landing system has the greatest impact on the system reliability. The reliability of soft-landing system can be significantly improved with the multi-inflation module, but the reliability of soft-landing system is not significantly improved when the number of inflatable module are more than two sets.