In order to solve the problem of large deformation in Muzhailing tunnel caused by soft rock under high ground stress, the numerical simulation was carried out to study the three-bench method. The characteristics of surrounding rock were grasped by analyzing the deformation and stress state of the surrounding rock after excavation. The results show that the main deformation of the surrounding rock has happened before the tunnel face comes and the deformation of tunnel face was large, which might become one of the main reasons lead to the large deformation of surrounding rock. Therefore, the advanced support of the surrounding rock needs to be strengthened during the excavation of tunnel to control the pre-deformation of surrounding rock and the deformation of tunnel face. The results of study can provide a reference for the similar construction of soft rock tunnels with large deformation.