Abstract: In order to explore the deformation and failure characteristics of mining floor at deep double-longwall face, based on the geological and mining conditions of the typical deep double-longwall face in complete area in Chengjiao Coal Mine, the groups of rock mass are divided; the 3D engineering geologic model for the double-longwall face is established. The distribution characteristics of the plastic zone and the maximum vertical stress are analyzed after fully mining in different floor depths; there are quite obvious zoning features for the two important parameters in the deepening direction of mining floor, and they have a good consistency in the aspect of judging the failure depth of floor, the failure depth of the mining floor at working face is about 27 m.