Due to the rapid development of the power industry and the reform of the power market, power companies put higher requirement on power economy. Network losses reduction, especially in the distribution network, has become an urgent problem that need to be solved. Using machine learning as an entry point and through data-driven method, based on different impact on line loss result of different flow, line loss model is built with artificial neural network (ANN), which realizes the theoretical calculation of line loss and electricity theft judgment. Through the relevant cases, the accuracy and reliability of line loss prediction and electricity theft analysis based on ANN model are proved.