Abstract: At present, the classification of nuclear power plant equipment mainly considers nuclear safety, and there is no equipment classification system aiming at economy. With the continuous development of the third generation of nuclear power plants are becoming higher and higher. As one of the most important economic indicators of a power plant, availability intuitively reflects the economic benefits of power plant operation. In this paper, a set of classification system based on availability is created, which classifies power plant equipment according to the influence of single equipment failure on the availability of power plant. By putting forward different technical management requirements for different equipment with different availability levels, the purpose of improving unit availability levels, the purpose of improving unit availability is achieved. This method is described from three aspects: identification of important equipment for nuclear power plant availability, classification of availability levels, and design management requirements for different availability levels. Finally, according to the different availability levels of equipment, relevant measures are taken to improve the availability of equipment from the aspects of design, manufacturing, operation and maintenance, quality assurance and so on, so as to achieve the effect of improving the availability and economy of the power plant.