Abstract: For the problem that manual observation method of underground water level in coal mine could not obtain variation of hydrological parameters overall and real-timely, an online hydrological monitoring system was used in Jinjie Coal Mine to obtain water level data of hydrological observation hole. The application shows that the system can monitor variation of coal mine hydrological parameters real-timely, which can be used to guide reasonable distribution of water discharging hole in working face, predict water inrush of working face with high precision and guide optimization of drainage system in working face, so as to decrease cost of water discharging engineering of coal mine.