Abstract: In order to solve the problem of large loss of coal resources in large coal pillars in fully mechanized top coal caving in extra-thick coal seam, there is a single method to determine the reasonable width of small coal pillars along the roadway, and there is a large gap between the research results and the actual project.Taking the Lingdong coal mine of Zhalainuoer mining area as the engineering background, the paper puts forward the small coal mining along the goaf in the extra-thick coal seam under multiple means based on the JW-6 underground high-frequency electromagnetic wave CT system, borehole stress monitoring system, numerical simulation, etc, comprehensive determination method of reasonable width of column.According to this method, the distribution and evolution of lateral support pressure in fully mechanized top coal caving in extra-thick coal seam in Lingdong coal mine are analyzed, and the reasonable width of small coal pillars in gob roadway for fully mechanized top coal caving in Lingdong coal mine is determined to be 7.0-10.0 m.The engineering practice results show that the width of small coal pillars in fully mechanized top-coal caving mining determined by this comprehensive analysis method is reasonable.During the mining, the deformation of the surrounding rock of the tunnel is mostly controlled within 300 mm, and the deformation is small, which meets the safety production needs of the working face and improves the recovery rate of coal resources.The research results have important reference significance for determining the reasonable width of the small coal pillars of the roadway driving along next goaf in extra-thick coal seam.