The invention is suitable for a key technology and a battery management technology of a million-kilowatt advanced pressurized water reactor nuclear power station, relates to an energy comprehensive optimizing technology for an energy system combined with the key technology and the battery management technology of the million-kilowatt advanced pressurized water reactor nuclear power station, and discloses a method and a system for supplying an emergency power supply to a nuclear power station. The method and the system provided by the invention can be used for resisting against a working condition beyond a designed standard working condition, such as a serious natural disaster of earthquake overlapped with tsunami, and the like which cannot be resisted by the traditional emergency power supply system of the nuclear power station. The method and system for supplying the emergency power supply to the nuclear power station provided by the invention are designed on the basis of a design standard and a standard beyond the design standard of the nuclear power station. The system can normally run in serious natural disaster which is beyond the designed standard working condition. The method and the system can be used for reducing the reactor core melting probability of the nuclear power station by 21.6% and promoting the safety of the nuclear power station.