Abstract: Economy is an important factor for the construction of underground nuclear power plants. It is usually considered that the cost of underground engineering is worse than that of the nuclear power plant. But the conceptual design of the underground nuclear power plant shows that the addition static investment of the underground nuclear power plant is less than 12% compared to the same size and same reactor type nuclear power plant on the ground, which is in the acceptable range. Since the cost for the decommission of the underground nuclear power plant by burring is only 30% of the immediate decommissioning, less people and cost for the nuclear security is required comparing with ground nuclear power plant, and it is possible to eliminate the contingency plan area, the overall economy of the underground nuclear power plant is better than that of the ground nuclear power plant.