The water inrush coefficient method is widely used in coal mines in China for evaluating the risk of floor water inrush due to its easy data and operation. However, the critical value of water inrush coefficient is not deep enough. Based on the analysis of water inrush coefficient method, the P - M relationship curve method (statistics) evaluation is better than the water inrush coefficient method, and with Tuanbo Mine as an example, through the comparison of similar coal mine, and collected some similar mine water inrush in working face and the safety of working face water inrush data were analyzed by the statistical point of view that the critical value of water inrush in Tuanbo Mine, the practice proved that the prediction accuracy was high, providing reference method for mine water prevention.