Abstract: As the force source of floor destruction,ground pressure is the main factor for the problem of confined water inrush.For studying coal floor damage depth and acquiring more knowledge of water-inrush mechanism,it's an important precondition to know the pressure distribution in the coal seam floor.The stope surrounding rock stress-strain relationship and goaf floor stress distribution in different stage has been analyzed by the simulation of FLAC.According to the vertical stress and strain in the floor of different depth,mathematical method was used to get stress-strain constitutive equations changing with stope depth.The result shows that with the increase of depth,the vertical stress is gradually increased,but vertical displacement reduced gradually.The floor vertical stress σy is a quadratic function of the floor depth X.The floor strainε in vertical is a negative exponential function of the floor depth X.