After mining, the goaf unloads and the floor below lateral wall is subject to abutment pressure, which results in the stress redistribution. Therefore, it is necessary to establish a new mechanical model for the mining floor strata regarding to the feature of the final stress field of surrounding rock, which is a superposition of in situ stress field and excavating stress field after the exploitation of coal seam. Then the analytical expressions of stress and displacement of mining floor are deduced, in which the Fourier integral transform is used to solve the biharmonic equation and the form function method is employed to solve dual integral equation. Furthermore, the Mohr-Coulomb criterion is applied to determine the plastic failure depth of floor strata as well. The results of the example show that principal stresses in goaf floor increase up to in-situ stress with increasing the depth, but the maximum principal stress in the floor below lateral wall decreases up to in-situ stress with decreasing the depth. When the depth is lower than 10 m, the minimum principal stress, , changes to be the intermediate principal stress due to the rotation of the principal stresses and further decreases with the increase of depth, while turns to increase with the continually increased depth, until up to in-situ stress. It is also found that the maximum upheaval of the floor in the central region of goaf can reach 0.236 m, while lateral wall floor moves downward due to the effect of abutment pressure on the lateral wall floor. The plastic failure region is shown to be greater in the middle than two edges and the greatest failure depth reaches 31.2 m, which is 1.04 times the half width of excavation. At last, the FLAC3D software is employed to simulate the excavation of coal seam. The tendency of simulation results compared with theoretical results is consistent except a certain departure. The proposed methods is proved to solve stress and displacement of floor accurately, which can provide significant guidance in practical engineering.