Aiming at the safety failure accident caused by the system dependency relationshipthis paper constructs a system safety network based on the dependency relationship according to the logic of “liveware-environment-software-hardware”and analyzes the mechanism of emergent failure of safety.A system safety network framework based on interaction behavior is establishedand the method of Functional Dependency Network Analysis (FDNA) is improved accordingly.Cascading failure is used to characterize the emergent failureand a numerical simulation method of emergent failure of aircraft system safety based on cascading failure is proposed.The evolution relationship between system components and interaction behavior is analyzed.The network damage mode under different failure modes is obtained.The simulation results show that：1) The emergent failure process of aircraft system safety needs to consider both the topology and the safety benefits；and 2) Emergent failure of safety can have a serious impact on system safety performance.