Abstract: After the Fukushima nuclear accident, the station blackout accident became a focus of attention. In order to study the system response of the nuclear power plant after the station blackout accident, a system-level model for the system and equipment of a passive nuclear power plant is established by using a system analysis code, and the calculation and analysis are carried out. The transient response of key parameters of the primary circuit system and the safety system is obtained, and the conclusions are as follow: After the station blackout accident,the passive nuclear power plant relies on the steam generator（SG） and the passive residual heat removal system（PRHR） can bring out the core decay heat in time. The PRHR start sooner or later affects the SG secondary side coolant to carry out the residual heat of the core, but it has little effect on the cooling capacity of the reactor core. The mass and flow rate of the coolant from CMT inject into the primary circuit have a great influence on the temperature, pressure and pressurizer water level. It can be considered to adjust the resistance of the CMT injection pipeline, so that the CMT injection flow rate is at a reasonable level to prevent the pressurizer from overflowing.