Abstract: In response to the technical challenges of supporting tunnels in loose and fragmented surrounding rock with poor anchorage, strong dynamic pressure, and strong structural stress influences, extensive on-site surveys were conducted, and several typical problems of large deformation in coal mine tunnel surrounding rock and difficulty in rock control were summarized and analyzed. Based on the analysis of existing support technologies and theoretical foundations, a concept and method for the rapid support technology of reconstructing high-strength load-bearing structures were proposed. Taking the 11205 down-hill transport tunnel at Longbao Coal Mine in Guizhou as an engineering background, the causes of deformation and failure were analyzed. A combined support method of displacement and unloading for fragmented surrounding rock was designed in practice. The design plan and optimal parameter calculations for the roadside backfill wall were carried out, and a mechanical model for the load-bearing capacity of the roadside backfill wall was theoretically established. Its load-bearing strength was analyzed to determine the strength of the wall and its suitability and effectiveness with the surrounding rock of the tunnel. By integrating the FLAC^3D numerical simulation software and the Python scripting language, the moth-flame optimization algorithm was applied to determine the optimal displacement parameters for the fragmented rock tunnel (wall thickness and unloading zone width). A new material for high-strength, high-toughness backfill support was developed. By displacing and reconstructing the weak wall body, the tunnel roof, backfill, and floor were reconstituted into an integral load-bearing structure. Industrial-scale trial results underground showed that after reconstructing the weak rock body of the tunnel, the new structure consisting of the roof, backfill, and floor fully utilized the surrounding rock’s own load-bearing capacity and resistance to deformation. The rock deformation stabilized, the convergence rate was generally less than 0.2 mm/d, with no significant deformation, and the results of the numerical simulation calculations were consistent with the engineering practice monitoring, indicating that the roadside backfill displacement support scheme has a good effect on controlling tunnels in loose and fragmented surrounding rock. This can provide a theoretical basis for the support and strength parameters of roadside backfill. Finally, the paper looked forward to deeper research into the technology of rapid support for reconstructed load-bearing structures.