Abstract: With the increase of mining depth, the trend of water-surge disasters above the pressurized aquifer is increasing year by year, which seriously threatens the safe mining of coal seams, especially the bottom plate of deep-mined extra-thick coal seams. In order to study the deformation and damage characteristics of the bottom plate of deep mining extra thick coal seams, taking Dongwan Coal Mine in Shanxi Province as the study area, the distributed fiber optic sensing technology (BOTDR) was used to obtain the axial strain curves of different depths of the working face under the bottom plate of the coal seams, and the three-dimensional resistivity method was used to obtain the characteristics of the distribution of its resistivity, which was then compared comprehensively with the monitoring data from monitoring drill holes. The results show that the comprehensive monitoring technique can effectively identify the stress excess, deformation and damage characteristics of the rock during the working face mining process, the influence range of mining overstress is about 36 m, the depth of damage of the coal seam bottom plate is about 12 m, and the depth of deformation of mining disturbance is about 26 m. The influence of the stratum structure and the lithology is the main reason that the deformation of the coal seam bottom plate is manifested as a layered characteristic. The monitoring technology can effectively capture the fine features of the deformation and damage of the coal bed floor, which is of great value to the deep mining of extra-thick coal bed floor.