Abstract: In the process of deep coal seam mining, confined water pressure and complex structural environment are important factors threatening mine safety production. In order to study the water inrush law of floor under the influence of fault on confined water, based on the basic mechanical principle, the mechanical model of surrounding rock under the influence of coal seam mining on confined water is established to solve the critical water pressure of fault water inrush. At the same time, based on the control variable method and fluid solid coupling theory, using FLAC^3D numerical simulation software, from the perspective of the joint coupling of stress field, displacement field, seepage field and failure area, the water inrush law of coal seam floor under different fault shape and confined water pressure is analyzed. The results show that when the working face is mined near the fault area, the fault dip angle has a great influence on the vertical stress on the surrounding rock. When the dip angle changes from 30° to 60°, the average change rate of the vertical stress is about -29%; the fault width mainly affects the damage degree of the fault near the bottom of the working face. The wider the fault width, the smaller the damage degree; the aquifer water pressure plays a leading role in the pore water pressure in the fault. The greater the dip angle and the smaller the width of the fault, the higher the pressure of confined water in the aquifer, and the stronger the risk of water inrush in the floor.