Based on the hydrological and climatic data(from 1951to 2014)of the three outlets of southern Jingjiang River system and the analyses of environmental changes,this study quantitatively analyzed the contribution rates of climatic factors and human activities on the changes of runoff volume at different time scales.The results are shown as follows:(1)Environmental changes,marked by the decrease in rainfall amount of the three outlets of Jingjiang River and the surrounding areas,the reduction in runoff of Yangtze River and the water level lowering,as well as the fluctuating increase of no-flow days of Jingjiang River,led to the gradual decrease in runoff of the three outlets of southern Jingjing River.(2)The runoff amount of the three outlets of southern Jingjing River changed with the fluctuant increase and decrease along the long time series,but it gradually lowered in different time scales.The turning-point years of runoff and rainfall amount were 1958,1972and 1998.(3)On the basis of 19511958,the contribution rates of rainfall fluctuation to the variation of runoff in 3periods(19591972,19731998and 19992014)were 26.71%,2.9% and 7.05%,respectively,while the contribution rates of human activities,which were mainly the large-scale water conservancy projects,were 73.29%,97.10%and 92.95%,respectively.