<p>The deformation and failure of deep soft rock tunnels are driven by energy. Few scholars have focused on the energy transfer mechanism between the surrounding rock and tunnel support. This study develops an energy calculation method for surrounding rock based on the Mohr–Coulomb strain-softening model. Building on the analysis of energy distribution and evolution within the surrounding rock, the interaction between the surrounding rock and tunnel support is further explored from an energy perspective. The results demonstrate that excavation unloading continuously transforms far-field input energy into elastic strain energy until its limit is reached. Beyond this threshold, excess energy is dissipated and released through plastic deformation, with a portion of the energy being transmitted outward via the work done by the rock pressure at the tunnel boundary. Soft rock tunnels exhibit larger convergence displacement and higher work done by the rock pressure following excavation unloading, indicating that the performance of soft rock tunnels should not be assessed solely by changes in strain energy (internal energy) of surrounding rock. Under identical support timings, increasing the support stiffness reduces the energy required to be absorbed by the support and improves its ultimate energy absorption capacity. In contrast, delaying the support, while maintaining the same stiffness, reduces energy required to be absorbed. Based on these findings, a support design strategy is proposed to ensure that the energy required to be absorbed remains within its ultimate energy absorption capacity. The feasibility of this approach is verified through a case study analysis. While similar outcomes can be achieved using other methods, such as the convergence–confinement approach, the contribution of this study lies in providing a novel perspective on the interaction between surrounding rock and tunnel support.</p>