The forest ecosystem consists of gigantic canopy, thick forest litter, abundant roots and porous soil, and thus plays a critical role in soil and headwater conservation in mountain area. A forest ecosystem has different aspects of soil and water conservation functions in intercepting rainfall, adjusting river flow, reducingevapotranporation, amending forest microclimate, improving soil structure and reducing soil erosion, etc. One of the important goals of the ecological construction and vegetation recovery Beijing mountain are is to improve soil and water conservation capacity in this area. In order to offer better recommendations for soil and water conservation of forest ecosystems in Beijing metropolitan area, integreated evaluation of water and soil conservation capacity of the forest ecosystem is needed. Since 1990s, a number of water and soil conservation related criteria have been measured during growing season (May to October) at Beijing Forest Ecosystem Study Site. We collected and analyzed monitoring data of rainfall, forest canopy interception, water-holding capacity of forest litter, surface runoff, and soil loss during 2005-2008. The data collections were from four forest types: Liaodong oak (Quercus liaotungensis koidz), Huabei larch(Larix gmelinii var. principis-rupprechtii), Chinese pine (Pinus tabuliformis), and mixed deciduous broadleaf forest. Our results show that Liaodong oak forest had the highest canopy interception percentage (19.23%), followed by mixed deciduous broadleaf forest (18.33%), Chinese pine forest (13.29%) and Huabei larch forest (12.28%) during the rainy season. The water holding capacity of litter was highest in Liaodong oak forest (483.31%), and lowest in Chinese pine forest (362.63%); the water-holding capacity of soil was in order of mixed deciduous broadleaf forest (459.4mm), Liaodong oak (427.9mm), Chinese pine forest (418.8mm) and Huabei larch forest (407.5mm); the initial infiltration rate of the soil surface layer (0-80cm) ranged from 13.75 to 30.23 mm/min. The stable infiltration rate of soil water was mixed deciduous broadleaf forest (24.27mm/min) > Liaodong oak (20.19mm/min) > Huabei larch (10.55mm/min) > Chinese pine (8.36mm/min); the surface runoff of Chinese pine (4.37mm) was higher than other forest types, and the soil oss was the highest in Chinese pine forest as well. The integrated soil and water conservation capacity was in order of mixed deciduous broadleaf forest > Liaodong oak forest > Huabei larch forest > Chinese pine. The evaluation value (0.1039) of mixed deciduous broadleaf forest was much lower than other forest types. The deciduous broadleaf mixed forest had more abundant trees, more abundant underneath shrubs and grasses, and more forest litter; therefore its soil and water conservation capacity was the highest among the four forest types.