Abstract: In order to analyze the countermeasures for the accident of loss of AC power plus loss of ultimate heat sink, the integrated model of an advanced PWR has been built. As to the accident of loss of AC power plus loss of ultimate heat sink, the mitigation effect of different countermeasures has been analyzed. The results show that in the accident of loss of AC power plus loss of ultimate heat sink, if the steam-driven auxiliary feed water pump works, the heat can be removed effectively and the pressure, temperature and water level of the primary coolant system（PCS） will remain stable. If the passive residual heat removal system（PRS）works, the heat can be removed effectively, the pressure and temperature of the PCS will descend and the core will be covered all the time. If both the steam-driven auxiliary feed water pump and the PRS fail, the pressure and temperature of the PCS will rise and the core will be uncovered, which may lead to the damage of the core. The results also show that the time available for answering the accident of loss of AC power plus loss of ultimate heat sink is different in the cases of different countermeasures. This study can offer technical support for improving the key technique of advanced PWR.