Based on the data observed for debris flow and precipitation from 1995 to 1997 in Jiangjia gully,Yunnan Province,different weighted relations between antecedent rainfall and process precipitation are analyzed.The analyses indicate that antecedent rainfall and process precipitation are the critical factors to trigger debris flow.Debris flow may be divided into three types based on different weighted relations between antecedent rainfall and process precipitation.Moreover,the relation between sediment yield of debris flow and rainfall under different rainfall conditions is discussed and a sound result is obtained.