Abstract: Troditionally the coal mine water occurrence monitoring is applied to monitor the coal floor water outburst during coal mining.It is not reported that the monitoring system is used to forcast the roof water flooding or flooding caused by the incompact of Quaternary sand conglomerate aquafer and marine water. According to the hydro-geological condition of Longkou mining area the monitoring and forecasting system,which is base on the roof aquafer water level and water quality is established.The system can forecast the coal flooding before the Quaternary underground water or marine water breaks into the coal mine,resulting in the managing measures can be taken to get rid of the hazard.