Abstract: In order to assess the water conservation ability of main forest in Beijing mountainous area, the hydrological effect of the litter layer and soil layer of 3 typical tree species(Quersus variabilis, Pinus tabulaeformis, shrub) were studied. The results showed that the total litter layer storage of 3 typical tree species was about 12.93～32.67 t/hm2. The Pinus tabulaeformis forest was the largest and the shrub forest was the smallest. The litter maximum water-holding capacity and effective interception from large to small were Quersus variabilis forest, Pinus tabulaeformis forest, shrub forest. The soil capillary porosity of different forest types, decreased with the increase of the soil depth, ranged from 30.5%to 38.1%, which shows a large to small rank of Quersus variabilis forest, Pinus tabulaeformis forest, shrub forest. The maximum water-holding capacity of Quersus variabilis forest was 3 621.0 t/hm2 and noncapillary porosity water holding capacity was 816.0 t/hm2,followed by Pinus tabulaeformis forest and the shrub forest.Moreover, water holding capacity of litter had a correlation with immersion time(Q=alnt+b). Water absorption rates showed a power function with soaking time(V=ktn). Based on the analysis of litter and soil water retention characteristics of 3 typical tree species, it was found that the water holding capacity of Quersus variabilis forest was the best.