The occurrence of debris flow is affected by many factors. Risk zoning of debris flow plays a vital role in the early-warning and prediction of abrupt geological hazards, and exploration of new method is needed in the early-warning and prediction of geological hazards. The extension theory is a new method to solve contradiction matters. Based on extension theory, AHP and GIS, the risk zoning model of debris flow was established in this paper. The result of this research provides a new way in the risk zoning, early-warning and prediction of debris flow.