The integration of hydrological model system with GIS and remote sensing technology will be the prevailing trend in the study of hydrological cycle or processes in the future.The main purpose is to simulate the productive mechanism of runoff over the Baohe catchment located in the upstream of the Hanjiang River using hydrologic modeling system HEC-HMS,which includes several kinds of modules.Then DEM,soil data,landuse and landcover are processed synthetically using Geo-HMS(extended module of HEC-HMS),which can be embedded in ArcView3.2 software,and some important parameters in this hydrologic model system could be gotten.In succession,a sort of watershed modeling scheme with network elements is established after selecting and integrating the simulated algorithms of each hydrologic process.The result shows that the simulated flow agrees well with the observed flow at the Jiangkou station,the outlet of the Baohe catchment.