[Objective] To evaluate water production function quantitatively and study its spatial expression of watershed ecosystem in order to provide scientific support for optimal allocation and sustainable management of water resources and improvement of ecological efficiency.[Methods] Taking the upstream catchment of Daling River as the study area, we firstly evaluated the water conservation service in 2015, and analyzed the spatial distribution characteristics using the water yield module of integrated valuation of ecosystem services and tradeoffs (InVEST) model. Then, the obtained water conservation evaluation results were normalized and divided into different classes.[Results] ① Total water conservation capacity of the upstream catchment in Daling River reached to 1.82×10⁹ m³ in 2015, and it showed obvious spatial heterogeneity. ② The normalized results showed that high grade area of water conservation was located in the central and northern part of the Kalaqin Left Wing Mongol Autonomous County, while low grade area of water conservation was located in the northern part of Aohan and Ningcheng County of Inner Mongolia and Pingquan County of Heibei City. Moderate grade area of water conservation was widely distributed, which accounted for 34.7% of the study area. ③ The Kalaqin Left Wing Mongol Autonomous County and the southwest part of Chaoyang City was important water conservation area, which should be strictly managed and protected.[Conclusion] Factors such as land use type, climate and soil texture have important influences on the heterogeneity of water conservation, the spatial distribution of water conservation is uneven and the difference is significant.