Abstract: From the view of system theory, this paper uses the analytic hierarchy process (AHP) to analyze the factors which affect debris flow then ten factors from conditions of debris flow material source, terrain conditions and predisposing factors are quantified to establishe hierarchy indicators system of debris flow risk assessment, and gives weight each factor. Finally, the evaluation results has a high relativity to the fact is verified by example test. Therefore, the use of AHP for debris flow risk assessment is practical and effective.