Abstract: Zhouqu "8.8" Sanyanyu debris flow is a typical disaster occurred at deep valleys with high and steep rock side slopes in south of Gansu Province.How to mitigate the risk of this kind of debris flow is a subject valuable to research on.This thesis summarized the principles and methods that mitigate the debris flow on the basis of risk-reducing ideas.It analyzed the practical problems that the Zhouqu debris flow mitigations have to face,which includes the limited environmental capacity,the difficulties to relocate the town,and the psychology of local people after this catastrophe.Thinking of these practical problems,the author proposed the comprehensive mitigations which are partial evacuation plus engineering countermeasures plus monitoring early warning plus education for local resident,and made a relevant detailed explain for each of mitigation measurements.