Abstract: This paper presents the application of the grouting sealing technology on karst high-pressure water inrush in a deep-buried extra-long tunnel of the highway from Dejiang to Wuchuan in Guizhou Province. Firstly, some relevant issues are addressed such as the drilling equipment, grouting material selection and implementation of this technology. For different types of high-pressure water inrush, e.g. two-hole connected, single-hole independently exposed, and single-hole independent unexposed, different methods such as drainage pressure back-blocking, grouting stopping wall combined with axial and radial blocking, and advanced pre-grouting are adopted respectively. Consequently, the problem of high-pressure karst water inrush at multiple sections of the Dejiang tunnel has been successfully solved, so that the tunneling work can be restored, the safety of the project is guaranteed, and the construction period is shortened, which yields good economic and social benefits.