In the face of increasingly complex aircraft systems, the traditional safety analysis methods are insufficient for identifying unsafe interaction behaviors and hazard sources among complex systems. In order to effectively evaluate the safety of aircraft systems in the continuous airworthiness phase, an improved system theory process analysis (STPA) safety analysis method and evaluation model that integrates STPA and dynamic fault tree (DFT) were proposed. STPA was used to identify unsafe control behaviors and causal factors, which were integrated with dynamic fault tree analysis method. The accident causation theory was used to optimize the causal analysis method, calculate the probability of unsafe control behaviors occurring, and determine the key causal factors of potential system hazards. The results show that the improved STPA analysis method can accurately identify and analyze system hazards and support the safety analysis in the continuous airworthiness phase.