Abstract: In view of the problems of complex foundation structures, settlement sensitivity and others of high-fill areas in the goaf of Xinglongzhuang Coal Mine, as well as the characteristics of high demand for engineering bearing capacity, directional adaptation research is carried out by adopting the composite reinforcement technology of Subgrade Dynamic Densification with Casting (SDDC). By constructing a pile-soil collaborative bearing system, optimizing ultra-deep hole forming and high-energy tamping parameters, controlling the pile body formation and whole process quality of variable cross-sections, the bearing stability of foundation is improved. The results indicate that the bearing capacity of the composite foundation meets the design requirements, the settlement control is stable, and the feasibility and adaptability of the technical scheme are verified, providing engineering support for the ground facilities in the mining area.