Abstract: A mathematical model for the process of possible accident sequence in the CPR1000 nuclear power plant was established, and the Monte Carlo method was used to programming codes to calculate the possibility of timely recovery of AC power in each accident process. According to the calculation results, probabilistic safety analysis (PSA) of the station black out (SBO) was conducted in the paper. The results show that using Monte Carlo method to analyze the process of SBO can make the PSA more in line with the actual situation of the nuclear power plant. And the overall risk of the nuclear power plant and the risk of SBO can be understood better by using the method.