Abstract: Aiming at the problem of frequent single-phase grounding in 10kV ungrounded power distribution system, a fault line selection method based on zero sequence charge is proposed. First, the equivalent model of the 10kV ungrounded power distribution system is analyzed to obtain the changing characteristics of the zero-sequence current under a single-phase ground fault, and based on this, a zero-sequence charge fault line selection method for fault lines and non-fault lines is constructed; then Matlab/Simulink is used to build a 10kV unconnected power distribution system. The simulation model of the ground distribution network system was carried out and simulation verification was carried out under different working conditions. The results show that this method can achieve accurate line selection of fault lines, and has certain anti-transition resistance and anti-interference capabilities. It can provide technical support for the rapid location of single-phase ground faults in 10kV ungrounded distribution network systems.