Abstract: The dynamic reliability evaluation method can simulate the continuous or multiple changes of the system state, and becomes a new development point for the probability safety research of nuclear power plants. Based on the dynamic reliability evaluation method, the state black out process of the AP1000 by MAAP severe accident program was analyzed, the results were applied to level 2 probabilistic safety assessment (PSA) analysis and finally the effect on radioactive fission products was evaluated. The research results show that the dynamic characteristics of the system have a certain impact on the analysis results of the PSA of nuclear power plant, and the dynamic reliability evaluation process can mine more information, and to better guide the design of nuclear power plants and improve the safety of nuclear power plants.