Abstract: The stability of the bottom drainage roadway plays a key role in improving the gas extraction efficiency of adjacent coal seams. Based on the engineering background of II1 coal seam floor drainage roadway in Zhaogu No.2 Coal Mine, the characteristics of mine pressure behavior of roadway surrounding rock were obtained through field investigation and monitoring. Based on the theory of semi-infinite plane body of elastic mechanics, the stress solution model of coal seam floor under primary and secondary disturbance of upper adjacent layer was established, and the three-dimensional stress distribution and evolution characteristics of floor were obtained. Based on the full plane strain model, a three-dimensional mechanical model of the bottom drainage roadway is constructed. The implicit analytical solution of the plastic zone boundary of the rectangular roadway considering the axial stress and out-of-plane shear is derived. The size and morphological characteristics of the plastic zone of the bottom drainage roadway are quantitatively analyzed. The deformation and failure mechanism of the surrounding rock of the bottom drainage roadway is revealed, and the targeted support countermeasures are proposed. The research shows that the high ground stress and the multiple disturbances of the upper adjacent layer cause the bottom pumping roadway to be in a high deviatoric stress environment, and the distribution of the stress direction of the floor shows a rotation characteristic. The stress deflection angle of the center point of the bottom pumping roadway is 47.49°. The plastic zone of the roadway roof shows a malignant expansion, and the overall plastic zone of the surrounding rock shows a “butterfly-like”asymmetric failure characteristic. Compared with the complex variable analytical method proposed in this paper, the plastic zone size estimation of the traditional equivalent circle method has obvious deviation, and cannot reflect the asymmetric characteristics of surrounding rock failure, which verifies the rationality of the theoretical model in this paper. In view of the deformation and failure characteristics of the surrounding rock of the bottom drainage roadway, a large elongation impact-resistant flexible anchor cable was developed, and an optimized support technology of“anchor net cable spray”was proposed. The field industrial test results show that the optimized support scheme can effectively control the large deformation of the surrounding rock of the bottom pumping roadway. During the service period, there is no breakage of the anchor cable, and the integrity of the support structure is good, which ensures the stable operation of the bottom pumping roadway.