Abstract: Based on the mature technology of self-reliance 600 MW nuclear power plant design, and the construction feasibility study of large-scale underground nuclear power plants, the underground plant CUP600 with new models and technical scheme of independent intellectual property is developed and proposed for the first time in China, forming a complete set of engineering key technology. The evaluation demonstrates that the safety of this underground nuclear power plant is high, the construction technology is feasible, and the economy is reasonable with specific features of the fourth generation nuclear power technology, which fully meet the requirements of the latest nuclear safety standards of the state.