Fault location of dc distribution network is the key to fault diagnosis, line safety and power supply quality. This paper first studied the high-voltage direct current transmission and fault location techniques in ac power distribution, then based on the voltage source inverter dc micro network analyzes the single fault and failure response of the electrode short circuit fault features, finally puts forward a way to use converter outlet side capacitance discharge process, extraction of fault voltage circuit inductance value calculated by current information new method to determine the fault location. The fault process is segmented according to the voltage relationship, and the fault line selection is carried out by using the rate of change of transient current. Finally, the fault location is determined according to the second-order response process of the fault circuit. Simulation results in PSCAD/EMTDC show that the location algorithm can accurately identify fault types and fault lines and locate the fault location. The positioning error of inter-electrode short-circuit fault is within 0.5% and that of single-electrode grounding fault is within 3%.