Due to special topographical, geological and meteorological conditions, debris flows occur frequently and result in heavy losses of lives and properties in mountainous areas, which become a great threaten to the sustainable development of regional economy and society in western China. At present, debris-flow prevention has performed well in many mountainous countries and has made headway in early warning, disaster mitigation by structural engineering methods, and risk analysis and management. In this paper, debris-flow prevention techniques have been introduced from the aspects of botanical methods, geotechnical engineering methods, and synthetic prevention system based on the above two methods. In addition, the treatment system of multilevel runoff and unconsolidated soil in the catchment with a chain of “slope–gully–valley” is set up in consideration of sediment load of main rivers, incorporation of slope improvement and gully retention, as well as micro-site factors for matching species with the site. Furthermore, attentions should be paid to the mechanism and technical details of vegetation measures for debris-flow prevention, as well as effective incorporation between botanical method and geotechnical method.