The invention relates to a coolant nitrogen-charging design capable of realizing substantial corrosion prevention and explosion protection for a nuclear power plant. The coolant nitrogen-charging design comprises a nitrogen-charging design of a pressurized water reactor, a boiling-water reactor, a heavy water reactor and a gas cooled reactor for corrosion prevention and explosion protection, and is a key issue for effective nuclear energy utilization and nuclear power safety and a hot subject for reactor optimization design research caused by painful lessons of explosion of the Fukushima Daiichi nuclear power plant. Nuclear power designers pursue for a one-hundred-percent safe design with decades of efforts. Serious problems are generated due to unreasonableness of a key design in an emergency shutdown system and a coolant system for reactor meltdown prevention and hydrogen explosion protection, e.g., boric acid should not be used, while boron salt with high content of boron should be chosen; furthermore, the coolant system should be designed to charge nitrogen, but not hydrogen. Thus, reactivity can be effectively controlled; corrosion can be inhibited; and generation of hydrogen is reduced, and hydrogen explosion is prevented. Through synergistic effect of a neutron absorber added into a coolant and a spent fuel tank with nitrogen, and chemical combination of hydrogen and nitrogen, the purposes of corrosion prevention and explosion protection are cooperatively achieved. Thus, the optimized nitrogen-charging design for the nuclear power plant can achieve safety and stability of the nuclear power plant, and can obtain unexpected additional benefits from corrosion prevention and hydrogen explosion protection.