The invention discloses a large nuclear power station with underground reactor and radioactive auxiliary plant. The large nuclear power station comprises a nuclear island and a conventional island, wherein the nuclear island generates steam by nuclear fission, the conventional island uses the steam generated by the nuclear island to generate electricity, the large nuclear power station is characterized in that the nuclear island is arranged in a underground cavern group excavated in hard rocks by men, the conventional island is on the ground, a passive pool is arranged at the upper part of the cavern group, and a nuclide migration protective system is also arranged outside the cavern group. The large nuclear power station is consistent with the passive concept of the third generation of nuclear power technology, effectively prevents nuclear radiation diffusion in accidents, has the good resistance to shock, prevents tsunami and typhoon from damaging nuclear buildings, has the good safety, and can resist the terrorist attack.