Abstract: Coal-based solid waste stockpiling in large scale occupies land resources and causes severe environmental pollution. Exploring green and efficient pathways and models for solid waste utilization is a crucial measure to ensure the high-quality and sustainable development of coal energy bases. Using the efficient phosphorus-solubilizing strain Pseudomonas sp. BBS-A and Dark Septate Endophytes (DSE), a study was conducted with a substrate composed of 30% (mass fraction) coal gangue and sandy soil. Four treatments were established: a non-inoculated control group (CK), inoculation with BBS-A, inoculation with DSE, and dual inoculation (B+D), to investigate the effects of microbial activation on soil nutrient availability in coal gangue and the growth of Medicago sativa L.. The results showed that inoculation promoted the release of nutrients retained in coal gangue, significantly enhancing soil nutrient availability and enzyme activity. Particularly under dual inoculation, the electrical conductivity, available phosphorus, and available potassium contents in the coal gangue-sandy soil substrate increased by 164.02%, 38.01%, and 80.00%, respectively, compared to the CK. Inoculation significantly promoted the growth and root development of alfalfa, with the overall performance across different inoculation treatments being: B+D > DSE > BBS-A > CK. Mantel correlation analysis revealed significant correlations between enzyme activity, total potassium content, photosynthetic characteristics in the microbial-activated coal gangue-sandy soil substrate, and bacterial community structure. Compared to CK, the dual inoculation treatment significantly increased the bacterial Good’s coverage index, with significant differences in environmental factors and bacterial α-diversity. The DSE group significantly enhanced fungal Shannon and Simpson indices. In conclusion, functional microbial activation accelerates nutrient release from coal-based solid waste, providing a nutritional source for plant and microbial growth, improving the ecological environment of mining areas, This will provide theoretical foundations and technical support for the efficient utilization of coal gangue and ecological restoration in mining regions.