In order to obtain the real-time hydrological information, and conduct the analysis and early warning on hydrological data, this paper studied the water level acquisition algorithm, used the dissection method to make the water level more accurate, optimized through image refining to reduce the complexity of the algorithm; it designed the data acquisition module of water level detection system, realized the real-time data transmission through programming, used Microsoft Access database to exchange data between server and communication module, manipulated data in the database, and designed the human-computer interaction interface; experimental studies have shown that this system can have access to information in a real-time and accurate way, and has the functions of warning, settlement &accumulation, statistical analysis and so on, which effectively improves the water level monitoring automation and control level, and helps to improve the management level of the hydrological industry.