Abstract: Through floor unloading pressure and floor hole wall deformation observation in 203 working face, and detection of drilling gas concentration and gas pressure changes, the study of coal mining working face floor relief deformation law is carried out. The results showed that: when the working face pushes forward to about 10 m from the bottom drilling, the bottom pressure is relieved and cracks begin to develop; as the coal mining working face pushes through the bottom drilling, it gradually moves away from the bottom drilling, and the relief pressure range of the bottom gradually expands to the depth of the bottom, and the deformation and damage of borehole are more and more serious. Within the range of 10 m to 30 m behind the goaf and 10 m to 30 m below the working face bottom plate, the maximum pressure relief deformation and a large amount of gas (oil-type gas) gushing occurs. Based on this, the technical parameters of gas extraction in floor coal seam and oil and gas layer of 205 working face are optimized.