Abstract: To address the new challenges brought by large-scale distributed generation（DG） grid connection to fault location in distribution networks, an active distribution network fault section localization method based on adaptive immune algorithm is proposed. Based on adaptive immune algorithm for fault segment localization, it effectively reduces the probability of traditional immune algorithms falling into local optimal solutions in the case of distorted fault information. Firstly, an innovative nonlinear adaptive cross mutation operator improvement strategy is introduced to establish an adaptive immune algorithm function calculation model suitable for distributed power generation access. Then, based on this algorithm, the remote signal information of each feeder terminal unit（FTU） node is processed to quickly and accurately locate the fault section. Based on MATLAB,simulation tests were conducted on an IEEE 33 node distribution network with DG,and the test results showed that this method significantly improved the speed and accuracy of fault localization.