Abstract: The large amount of coal gangue after washing in Dahaize Coal Mine not only increases the operation cost of the mine, but also causes environmental pollution on the ground to varying degrees. Under special circumstances, the problem of difficult treatment of coal gangue also seriously affects the normal production organization of the mine. In order to solve the problem of large amount of coal gangue stored in the coal mine, a million-ton coal gangue overburden isolation grouting backfilling mining technology is carried out in Dahaize Coal Mine. The principle of overburden isolation grouting backfilling technology is analyzed in detail, that is, the key layer to control surface subsidence is found in the stratum above the mining area, the grouting filling mining parameters are designed based on the principle of no breakage of the key layer, and the solid waste materials such as coal gangue are used to form a compacted bearing structure to support the key layer, so as to effectively control the movement of rock strata and surface, reduce ground collapse, and Combined with the special conditions and challenges of post-mining grouting in Dahaize Coal Mine, the project overview, process flow, grouting drilling and filling parameters are studied, and the technical, economic, environmental and social benefits of the project implementation are evaluated. The overburden isolation grouting backfilling technology of coal gangue overburden rock effectively reduces the ground stacking amount of coal gangue, reduces the occupation of land resources and the pollution to the environment. At the same time, the establishment of a million-ton coal gangue treatment system, the maximum processing capacity of gangue can reach 4000 tons per day, with the completion of the foreign gangue allocation and repair system, the annual processing gangue can steadily reach 1.5 million tons, improving the treatment capacity and efficiency of coal gangue, and realizing the resource utilization of coal gangue. Moreover, reducing the treatment price of gangue to less than 60 yuan has great economic benefits, and also innovates a green mining model of "gangue is not discharged, water retention mining, and surface sinking is reduced". This achievement not only provides a new technical path for mining under similar geological conditions, but also contributes effective strategies for environmental protection and sustainable development of mining areas.