Abstract: Aiming at the present situation that the pressure water threat brought by the continuous deepening of mining depth increases further, according to the specific geological conditions, the lifting of confined water and floor failure in different stages of exploitation were observed by using similar material simulation tests and self-designed confined water lifting simulation device. From the beginning of mining to the time of approaching fault, the laws of floor from slight damage to final water-conducting formation are deeply studied. The internal development of cracks was studied by the method of stratified dismantling of the model.