In view of Shiyang river basin ecosystem problems of water source supply and on the basis of study about inVEST model in home and abroad，the paper built InVEST model based on GIS and SWAT platform. InVEST model is the main method to estimate the water source supply amount. Through estimating the volume of water supply of ecosystem in Shiyang river basin, the paper found out the reason of temporal and spatial change of water supply service in Shiyang river basin.The precisive estimation of water supply of ecosystem has great significance for the service situation of water supply and the sustainable development of the basin,and can provide the basis for plan and management of the basin.