Abstract:When the water-pressure in floor stratum exceeds the floor strength after coal mining,the floor collapses and water-inrush from coal floor occurs. This phenomenon can be tackled by catastrophe theory. In the paper,a cusp catastrophic model of water-inrush from coal floor is established,and water-inrush mechanism of coal floor destruction is analyzed. The ratio of water pressure to stress, can be derived from the model. When >1,water-inrush from coal floor may occur. When <1,no water-inrush from coal floor occurs. The analysis of actual examples indicates that a cusp model is appropriate to describing the development of the ratio of water pressure to stress,and the prediction of water-inrush from coal floor is pertinent.