Gangou valley in Luding County,Sichuan Province,is a typical valley of moraine-supplied debrisflow.Source supply is complex in debris flow processes.Based on a field survey,the characters of its sourcesupply process are analyzed by taking the debris flow occurred in 2005as an example.Finally,source supplyis classified as the two types of initiating source and maintaining source and each type of the source supply isinterpreted.The research is helpful for us to understand the mechanisms,source supply process and hazardmitigation of moraine-supplied debris flow.