Abstract: The traditional line loss calculation method of medium voltage distribution network is not precise enough to effectively find the abnormal line loss. Based on the topology section model, this paper realizes the calculation and analysis of time and section division line loss through the correlation and fusion of minute level measurement data across business fields, such as D5000, distribution automation and power consumption information collection, and can accurately locate the abnormal time and section of line loss. On this basis, a fine sectionalization and anomaly location method based on portable measurement terminal is further proposed, which can make up for the limitations of distribution automation terminal distribution and solve the " last kilometer" problem of anomaly diagnosis. The effectiveness of this method is proved by the analysis of actual abnormal power consumption cases. The distribution line loss diagnosis and analysis system based on this method has been applied in Jiangsu Province and achieved remarkable results.