Abstract: To address the issues of limited land availability and increasing environmental pressure caused by gangue stockpiling at Baode Coal Mine, a overburden rock separation grouting backfill technology based on key stratum theory is proposed. This technique enables in-situ reinjection and resource utilization of coal gangue. By establishing a technical system of “key stratum stability control-separation space utilization-efficient grouting backfill”, industrial-scale applications have been implemented in working faces such as 81309, achieving an annual disposal capacity of 2.4 million tons. Field practice shows that the technology can reduce surface subsidence rate from 0.76 to 0.18, and lower the treatment cost to 70 yuan per tons, a 41.7% reduction compared to conventional methods. The engineering application effectively prevents key stratum fracturing, protects aquifer structures, and alleviates the ecological pressure caused by gangue dump expansion by reducing land occupation to a certain extent annually. An integrated disposal model of “gangue reinjection-subsidence control-green recycling” has been established, offering a replicable approach for efficient resource utilization and green mine construction.