Digital basin model is established on the basis of raster DEM data. The Xin'anjiang Model is applied to discharge modeling. To improve on the evapotranspiration calculation of Xin'anjiang Model, the Aerodynamics resistance method of SSIB which is a land surface model is used to replace the former K-coefficient method, which makes the land surface hydrological model more reasonable. The Shuiyangjiang River Basin in Anhui Province is chosen for the simulation of hydrological studying. The result shows that the improved model performs better than the former model in discharge modeling.