For recent years,runoff generation and hydrological processes in Hailiutu River basin have been greatly changed by climate change and human activity,especially water and soil conservation construction.In this study,the trends in precipitation,evapotranspiration(ET)and river runoff as well as the effects of precipitation change and human activity on runoff variation have been studied.The results showed that during 1960-2000,annual precipitation and river runoff,monthly precipitation and ET in September and October as well as monthly runoff in all months showed a significant decrease.In addition,peak flow and base flow had a large decrease.Under the joint influence of precipitation change and human activity,the mean annual runoff decreased by 35 million m3 from the baseline period(1960-1985)to the change period(1986-2000),which accounted for 60.9%and 39.1%of the total runoff decrease,respectively.Precipitation change played a primary role in the decrease of annual runoff whereas human activity,particularly water and soil conservation construction,also had remarkable impacts on runoff variation. For recent years, runoff generation and hydrological processes in Hailiutu River basin have been greatly changed by climate change and human activity, especially water and soil conservation construction. In this study, the trends in precipitation, evapotranspiration (ET) and river runoff as well as the effects of precipitation change and human activity on runoff variation have been studied. The results showed that during 1960-2000, annual precipitation and river runoff, monthly precipitation and ET in September and October as well as monthly runoff in all months showed a significant decrease .In addition, peak flow and base flow had a large decrease .Under the joint influence of precipitation change and human activity, the mean annual runoff decreased by 35 million m3 from the baseline period (1960-1985) to the change period (1986- 2000), which accounted for 60.9% and 39.1% of the total runoff decrease, respectively. Precipitation change played a primary role in the decrease of annual runoff but human ac tivity, particularly water and soil conservation construction, also had remarkable phenomenon on runoff variation.