Aiming at the problems of the existing quasi-distributed optical fiber sensing measurement technology, such as complexity, low accuracy and slow response time, a quasi-distributed optical fiber water leakage monitoring system with high real-time performance and lower cost is designed; the system is mainly composed of sensitive detection. It is composed of needle, low light detection unit, main control unit and data transmission unit. The lateral coupling effect forms a series of sensing probes after the LED light source is scanned. Light enters the polymer fiber through the lateral coupling structure. When the medium between the LED and the coupling structure changes, the coupling light intensity increases, and the output light intensity at both ends of the fiber increases accordingly, so the liquid leakage event can be converted into a coupling medium change To measure and cooperate with several other modules to complete the construction of a water leakage monitoring system; the results show that the designed fiber-optic water leakage monitoring system has the ability to detect and locate water leakage signals, and the positioning accuracy is less than or equal to 10 cm. Basically realize the functions of liquid leakage detection and leakage point positioning, which conforms to the characteristics of quasi-distributed measurement.