Abstract: Multi-scale pore-fracture structures are widely occurred in coal reservoirs, and serving as the main spaces for gas storage and transport. Restructuring these multi-scale pore-fracture structures to enhance fluid adsorption and transport behaviors is critical to the successful implementation of in-situ modified mining technologies for the safe and efficient extraction of deep coal and coalbed methane resources. To address the limitations of conventional stimulation techniques and the unclear modification mechanisms, the multi-scale pore-fracture structure of coal mass, from nano-pores and micro-fractures to macro-fractures, and their impact on gas desorption, diffusion, and flow are analyzed. Two core modification principles are proposed, one is enhancing desorption and transport by modifying the fluid occurrence state, and the other is improving the permeability by modifying the pore-fracture structure. Two multi-scale modification approaches are introduced, one is enhancing the desorption through competitive adsorption and thermal effects to reduce CH₄ adsorption capacity, and the other is enhancing the permeability through dissolution-induced pore expansion and fracturing-induced fracture creation. Using supercritical CO₂ (ScCO₂) as an example, the experimental results reveal the evolution of multi-scale pore-fracture structures in coal mass under ScCO₂ injection, involving adsorption swelling, dissolution, mechanical weakening, and fracture generation. These processes collectively affect the adsorption and transport properties of coal mass. A multi-field coupling framework is established to describe mass transfer across scales, and porosity–permeability evolution. This work provides a theoretical foundation for targeted reservoir modification to enhance permeability, and CO₂ geological storage in deep coal seams.