Based on the DEM (digital elevation model) of Jiangjiagou watershed,Yunnan Province,the watershed is compartmentalized into some sub-units according to landform by using Geographical Information System software. With the information data of land use,soil classification,hydrology,and meteorology,the fitting CN values for sub-watersheds are presented and the CN distribution map is drawn by the GIS software. The hydrograph of calculated runoff process by the SCS model and isochrones method is fitted well with observed runoff data. It shows that SCS model can be successfully used in Jiangjiagou watershed and simulated result can supplement observed data. This paper provides a method to study the distributed hydrological model in Jiangjiagou watershed.