In the construction of the high-slope tunnel of high-speed railway from Chengdu to Guiyang, large-scale deformation of soft rock in coal measure strata occurred in the long section, which caused great difficulties to the tunnel construction. Focused on the deformation, the design unit immediately carried out the rock sample analysis, geological analysis and renovation design together with engineering solution to ensure the successful construction of the high-slope tunnel. This paper systematically introduces geological environment in the tunnel region, characteristics of the deformed section and engineering measures for treatment. According to the analysis, it is concluded that the disease of deformation section is caused by the effect of crustal stress on the soft rock with low strength, expansibility of surrounding rock with groundwater and group-effect, and meanwhile points out that soft rock has the time effect of slow creep, emphasis should be put on the research on the crustal and rock strength. Strengthening the initial support of soft rock in deep buried section can be regarded as an effective measure to prevent deformation.