Abstract: After the distributed power supply is connected to the distribution network, the accuracy of the grounding fault judgment algorithm using the phase current mutation is reduced. In order to solve the above problems, the grounding fault section positioning algorithm of active distribution network based on phase transient power direction is proposed. By establishing the equivalent model of grounding fault transient phase voltage and current of active distribution network, the analysis results show that the direction of the fault current flows from the bus to the line, and the fault line fault point downstream of the fault of the transient power absolute value is negative. According to the above characteristics, the grounding fault positioning device and phase transient power direction algorithm is designed. The simulation verification results show that this method, in which the small current grounding system at the neutral point of the distribution network is used, can be adopted to reliably judge and locate the grounding fault position in the distributed power input and exit, and different access quantity and position in the case of uneven current. Related research and its design can provide reference for the development and application of grounding fault positioning technology of active distribution network.