Through discussion on the formation mechanism and the features of debris flow in Sanyanyu gully in Zhouqu county, the seriousness of debris flow disaster and necessity of its prevention are analyzed, A comprehensive controlling program is put forward,which is to take the blocked works as dominant measure, meanwhile to combine debris flow silting ground, draining channel and biological measure. After controlling works finished,there will be 3. 14 million yuan of disaster reductional benefit,and economic benefit will be produced per year, debris flow changes to usual flood flow and its threat to Zhouqu county town will be eliminated at last.