Abstract: In order to reduce the interference of small wave disturbances（noise）on transient current in the communication process of small current grounding system and the communication network burden caused by sampling frequency increase,and solve the problem of the asynchrony of feeder terminal unit on both sides of fault section,the paper proposes a method for locating the faulty section in the small current grounding system. By detecting the transient zero mode current on both sides of the faulty section,the extreme value is extracted,the attenuation degree is calculated,and the auxiliary localization is carried out with the polarity. This method can greatly reduce the data transmission of the transient zero-mode current at each detection point during the process of upload or mutual exchange.Numerical simulation results show the effectiveness of the method.