Abstract: GM(1,1) model was built up by gray theory to predict coal mine water discharge. Based on the floor water inrush data of a coal mine working face in Taiyuan Formation, the model accuracy was improved to 96.26 percent by increasing frequency of observation and data density. The comparison of forecast data and actual data indicated that the model was reliable. In order to strengthen the safety and supervision of the working face, a cap of abnormal data was set up with actual hydrogeological conditions and the drainage ability to obtain the prediction of water inflow, abnormal time and amount.