The invention belongs to the technical field of electronic information, and discloses an underground pipe network leakage real-time monitoring and leakage point positioning system and method based ona time domain reflection technology. A step pulse voltage signal is input into a detection line, and a high-efficiency signal analysis processing algorithm is used for analyzing a reflection signal toobtain the leakage position of an underground pipeline. The time domain reflection device has a function of transmitting a pulse signal and receiving a reflection signal, and is connected with a detection line and a computer control end. The detection line and a water delivery pipeline needing to be monitored are laid on the underground in parallel. In the process that the pulse signals are transmitted along the detection line, due to the fact that the reflected signals are collected and recorded due to the change of impedance, and the position of pipeline leakage can be accurately calculatedand calibrated according to the developed positioning algorithm. The system has the advantages that the detection speed is high, the influence of weather and external meteorological environments is avoided, the influence of pipeline materials is avoided, the influence of pipeline burying depth is avoided, and the system has higher precision and wider applicability.