Abstract: In order to solve the safe mining of confined groundwater, we propose paste backfill method in this paper for the inhibition of floor failure depth and reducing water inrush risk; for the geological condition that Daizhaung Coal Mine lower group coal 1160 mining zone bears the threaten of confined groundwater, using FLAC^3D three dimensional model, based on different banckfill body filling rate and filling body strength, stress distribution, plastic zone distribution and displacement distribution laws are simulated under different space width of advancing operation; simulation results show that when filling rate reaches to 95% and filling body strength eventually increases to 4 MPa, stress concentration factor of surrounding rock at coal face is about 2, deformation amount of roof and floor is 200 mm, and floor failure depth is about 4 m.