With the continuous construction of new power system, large-scale access of distributed generation to low-voltage distribution network is an important development direction of energy in China. Therefore, rapid and accurate determination of fault location under power grid fault conditions is very important to improve the utilization rate of new energy and improve the reliability of low-voltage distribution network. Then, the current fault location research mainly focuses on the transmission network and medium and high distribution network, but there is little research on the low-voltage four wire distribution system, especially the scenario of distributed generation connected to the low-voltage four wire distribution system.In view of this, this paper proposes a fault location method based on impedance ranging for four wire distribution system, and gives a detailed calculation method and its acquisition method. This method overcomes the problem that most fault location methods are difficult to apply in low-voltage distribution network. The physical concept is clear and can well meet the actual operation requirements of distribution network. Finally, the proposed algorithm is verified and the simulation results show that the algorithm has good performance. The research results of this paper will help to improve the fault location level of low-voltage four wire distribution system.