Nuclear Power Plant is a highly complex structural system with high safety requirements.Fault location appears to be particularly important to enhance its safety.Ant Colony Optimization is a new type of optimization algorithm,which is used in the fault location and classification of nuclear power plants in this paper.Taking the main coolant system of the first loop as the study object,using VB6.0 programming technology,the NPP fault location system is designed,and is tested against the related data in the literature.Test results show that the ant colony optimization can be used in the accurate classification fault location in the nuclear power plants.