By monitoring Miyun reservoir watershed for 5 years from 2001 to 2005,the study showed that: the average annul precipitation in watershed was 594.7 mm,mainly concentrating from June to August,and being 70% to 80% of the annual precipitation.The average annual surface soil moisture was 6.8%~11.3%,and the annual variation increased firstly and then decreased later,which was similar to that of precipitation.With the improvement of vegetation coverage,runoff and sediment yields in watershed reduced gradually,and setback ratio of vegetation reached 77%.By sampling inspection on water quality of watershed,the results showed that most indexes of water quality achieved the government standards of First water,while over-leveled indexes were total N content and P content.