[Objective] Based on the simulation analysis of rainfall-runoff process and non-point source pollution load in each basin, the impacts of ecological construction in small watershed on the hydrological process and pollution control effect of Miyun Reservoir watershed were eraluated in order to provide scientific basis for water source protection, integrated restoration of mountain, water, forest, field and lake in watershed and ecological environment construction.[Methods] Taking the Sheyuchuan small watershed upstream of Miyun Reservoir, an important drinking water source in Beijing, as the research object, the model of combining EcoHAT-LCM model with traditional large-scale non-point source pollution model were used to simulate and analyze the ecological construction effect of the small watershed.[Results] With the increase of rainfall, the proportion of adsorbed N and P load to the total pollution load increased gradually, while that of dissolved N and P load to the total pollution load decreased gradually. When the residential areas in small watersheds had small town-level garbage disposal rate and garbage access rate, the pollution load of N and P in rural life could be reduced by 28%, and the existing fertilizer application in economic forests could be reduced by 43.9% and 48.9% in agricultural production activities.[Conclusion] The influence of different frequency rainstorm on adsorbed N, P load is greater than that on dissolved N, P load in the study area. The ecological restoration measures had a significant effect on the reduction of pollution load of non-point source N and P.