Based on the reasoning and decision-making function of the expert system, a set of intelligent diagnosis system of line loss abnormality in the station area is designed. In this intelligent diagnosis system, the original data of power consumption in the station area is loaded into the expert system for intelligent diagnosis of line loss abnormality. The station area with abnormal line loss is identified and the cause of the abnormal line loss in the station area is analyzed. Then, the abnormal line loss information is stored in the database of abnormal line loss in the station area. Managers of electric power enterprises can view the abnormal information of line loss on the human-computer interface of the system. The application of the system improves the diagnosis speed and efficiency of line loss abnormality, and improves the intelligent management level of power grid.