Abstract: According to the aquifer distribution of No.3 coal seam in the floor of Xin’an mine,the paper studies the damage degree of floor during the coal seam mining process.The distribution law of "down three zones" of floor damage is determined though actual measurement of pouring water into boreholes and numerical simulation.The risk level of floor water bursting in working face is judged based on "down three zone" of floor.It is obtained that the complete rock zone of floor is small and the damage depth is 18~20 m with high floor water bursting risk.According to geological conditions and the damage situations of "down three zones" of floor,the paper puts forward prevention and treatment programs.