Abstract: Though the Heihe River is one of the largest inland rivers in northwest China,its water supply is far from adequate to meet the water demand.In order to practice water allocation,water saving irrigation,and integrated management of the water resource,a study was carried out to make use of TOPMODEL in simulating the hydrological processes of the Yingluoxia Catchment(10 009 km²)in Heihe region.Traditionally,only data from the end station of this area were used as grid data of the whole catchment.They couldn′t describe the spatial variation of altitude-dependent precipitation in such a large basin.Hence,based on DEM precipitation data from about 10 stations were interpolated by using the PRISM approach with major control factors such as altitude,landform and distance.On the premise that the comparison between the results of the interpolation and the data of field investigation showed improved precision.TOPMODEL was then used to simulate daily volume of runoff in the catchment with satisfactory results,being 70% or so in prediction precision.