To improve the construction quality and speed of prestressed anchor cables and promote the mechanized construction process in soft rock tunnels with large deformation, a case study is conducted on the Muzhailing highway tunnel. Then, based on the R&D of key technologies for the mechanized construction of prestressed anchor cables, test sections of the Wudu right line of the Muzhailing tunnel are selected by building a fully mechanized construction method for soft rock tunnels with large deformation using largescale key equipment, such as cantilever road header and multifunctional cable anchor trolley, to realize the integrated construction of drilling, installation, anchoring, and pulling of prestressed anchor cables. The following results are obtained from the case study. (1) The development and integration of key technologies for the mechanized construction of prestressed anchor cables realize the efficient and stable construction of prestressed anchor cables in soft and broken surrounding rocks. The construction quality of anchor cables is significantly improved, and the effective prestress of anchor cables is increased by approximately 100 kN. (2) The fully mechanized construction method of soft rock tunnels with large deformation does not require extra labor while significantly improving the construction quality and speed. The labor required for primary support is reduced by 1/5 compared with the traditional method, the construction cycling time of a single primary support is shortened by approximately 2 h, and the maximum reduction of convergence around the tunnel reaches 48.6%.