The paper selected the macro-scale areas of the source region of the Yellow River as an object and carried out discharge simulation with the distributed hydrological model,the SWAT model.Based on the analysis and process of DEM data,such as flow direction,a watershed borderline,a river network and sub-basins by automatically becoming,rivers,codes and areas of sub-basins,structure and topology constraint of the river network were gained with a format of grid cells.Annually and monthly measured runoff data of Tangnaihai hydrologic station from 1976～1985 were used to calibrate the simulation parameters and determine some basic parameters of the model.The simulation results are satisfactory and show that climate change is the main reason for discharge change of the source regions of the Yellow River.In twenty years of the 1980’s and the 1990’s,the discharge decrease due to climate change is 62.11×108m 3/s,which accounts for 108.72% of total discharge change,and the discharge increase due to land-cover change is 5.73×108m 3/s ,which accounts for 10.03% of that with grid cell.