Taking the Chaohe River Basin above the Miyun Reservoir as a study area,the influence of soil and water conservation measures on annual runoff was assessed quantitatively by the rainfall-soil and water conservation-runoff statistical model established on the basis of multiple regression analysis using historical annual runoff,annual precipitation and areas of soil and water conservation measures in the drainage basin during 1961-2005.The results showed that during 1961-1970,1971-1980,1981-1990,1991-2000 and 2001-2005,the average annual runoff-reduction effects were 2.54%,3.52%,28.71%,6.87% and 48.02%,respectively,with an average of 22.96% during 1981-2005.The average annual runof-freduction effect was the greatest during 2001-2005,intermediate during 1981-1990,and the smallest during 1991-2000.The runoff reduction effects of soil and water conservation measures were more profound in the drier period.