Chaohe River Basin is an important water source of Beijing.Due to the environmental change,a significant variation occurred to the rainfall-runoff relationship of Chaohe River Basin,and this change affected the regional water supply seriously.We analyzed the variation of rainfall-runoff relationship with the long-term hydro-meteorological data(from 1961 to 2014)of Chaohe River Basin,and established an empirical statistical analysis model to analyze quantitatively the impact of climate change and human activity on the runoff condition.The results showed that(1)the runoff changed drastically,and presented a marked dropping trend after 2000,whereas the precipitation showed an insignificant declining trend.(2)The relationship between rainfall and runoff changed abruptly in 1979 and 1998.(3)The runoff coefficient decreased significantly after 1979,and human activity kept a negative effect on runoff,and was always the more dominant factor as compared to climate change.(4)The contribution rate of human activity was-109.75%during 1979 to 1998 and-88.97%during 1999 to 2014,while the contribution rate of climate change was 9.75%during 1979 to 1998 and-11.03%during 1999 to 2014.