Abstract: To effectively control large deformation in soft rock tunnels, stiffness coordination control technology was introduced. An integrated theoretical framework oriented toward engineering design was established, and methods for calculating support resistance and determining parameters were proposed. On this basis, an integrated and visualized tunnel support design system platform was developed, achieving a complete theoretical closed loop from surrounding rock response and stiffness demand to support parameter matching, as well as quantitative output of support parameters. Field comparison tests were conducted in a large-deformation tunnel on a plateau. The results show that in the originally designed section, the overall support stiffness was insufficient, leading to issues such as steel rib distortion, shotcrete spalling, and surrounding rock deformation exceeding the limit. After adopting the support parameters optimized by the platform, the initial support structure remained intact without any failure, and the surrounding rock deformation was significantly reduced: crown settlement decreased from 82 mm to 22 mm, and sidewall convergence decreased from 332 mm to 119 mm. The effectiveness and reliability of the stiffness-coordinated support design theory and the system platform were validated, providing a new technical approach for the refined design of tunnel support structures.