The invention relates to a segmented troubleshooting method of a residual current over-limit fault, and mainly solves problems of difficult troubleshooting and low efficiency of residual current over-limit faults in the prior art. A method for segmented troubleshooting of a large residual current at a circuit side is proposed, on the premise of determining the troubleshooting range of a residual current value and constant ratios of 80% and 40% of the head-end and the terminal-end of an early warning threshold, the middle portions are set according to branch number gradually-decreased percentages, rural common transformers are arranged according to a power supply sequence from large to small, and fault troubleshooting is more rapid and accurate; besides, a method for segmented threshold setting of service mains is proposed, the method can perform calculation according to the cross section area of the service mains and a threshold setting coefficient, and operation personnel can rapidlyset and record the device threshold and perform fault judgment at the spot. According to the method, the troubleshooting efficiency of the residual current faults is improved, and safe and stable operation of a power grid can be effectively guaranteed.