A reliability evaluation method of relay protection system based on ant colony algorithm is proposed to solve the problem that the reliability of relay protection of substation is not uniform. After analyzing the substation relay protection system, according to the factors that need to be taken into account in the substation relay protection, the ant colony algorithm is used in the reliability analysis of the substation relay protection in the process of finding the food in the process of finding the food. Buildingthe shortest distance between the effective nodes of the substationand the reliability analysis model. Through the numerical simulation, the ant colony algorithm is used to build the model, and the validity of the method is verified.