Using the software FLAC3D, we simulated the rule of deformation and failure of deep stope floor due to working face mining. The horizontal stress, vertical stress, shearing stress, horizontal displacement, vertical displacement, and plastic zone distribution of mined floor are all simulated in both the advanced direction and the tilted direction of working face. Along the advanced direction of working face, the region of floor strata come into being a compression region, an expansion region, and a recompression region; their displacement decrease with the increase of floor depth. While along the tilted direction, the rock mass under the upper and lower two-side coal mass is in a compressive state, resulting in a vertical compressive displacement and forming a plastic zone of 12.3 m in depth. Considering the failure depth of floor, the working face water-inrush coefficient of Taoyuan Coal Mines is 0.082, which is 1.4 times of the critical value. Therefore, effective measures must be taken to prevent water-inrush from floor aquifer and to ensure the safe mining of working face.