In view of the high cost and low real-time performance of the low voltage distribution network topology structure, a new online check method for low voltage distribution network topology based on Pearson correlation coefficient and KNN algorithm is proposed. First, the similarity of the user voltage sequence curve is judged by the correlation coefficient of Pearson. The correlation coefficient algorithm is used to verify the correctness of the relationship between the transformer and the user in the platform area, then find out the users with incorrect relationship and check again. For the users who need to be checked again, based on the data of GIS system and Technical Guidelines for Distribution Network Planning and Design, the user sample set is generated. The KNN algorithm is used to analyze the clips to generate the user sample set, and then the correct platform area is checked by the user. Finally, the correctness of the algorithm is judged according to the results of the artificial field check. This work is supported by National Natural Science Foundation of China (No. 51277134).