Abstract: The deformation failure of the coal seam floor at 203 working face in Huangling No.2 Mine was simulated by using the numerical simulation software FLAC^3D on the basis of the analysis of acquisition of mechanical parameters and combined with the embedded FISH language operating charges in the software itself. The results showed that the stress concentration appeared on the coal wall at the ends of working face with the constantly advancing of working face, and the maximum stress concentration factor was 2.16. Floor deformation gradually reduced with the increase of distance from the coal seam floor and the maximum was 2.1 m. The maximum failure depth of floor in Huangling No.2 Mine was 21 m. The error range is between 0.8% and 2% compared with empirical formulas, which agrees well with the vertical position of abnormal emission point at 203 working face and shows that the simulation result is relatively reliable.