Abstract: The paper proposed a design scheme of fast fault positioning system of distribution network. The system uses pole-mounted fault monitoring terminal to recognize faults and control master station to position fault section, the both exchange data through GPRS communication processor; uses instantaneous over-current method to recognize short circuit fault and total current method to recognize grounding fault. For situations of missing and distortion of fault information, the system uses tristate identification method to improve traditional positioning algorithm of fault section. The simulation result shows that the improved positioning algorithm of fault section can accurately position fault under situations of missing and distortion of fault information, it has high fault tolerance.