Based on balanced relationship of supply and demand of water resources in1980and1990in West China,this paper balanceablly predicts supply and demand of water resources in3periods.By comparing the difference of water supply,demand,shortage and shortage ratio in1980and1990in West China,it systematically analyzes spatial change s in relationship of water supply and demand as well as their cause s.Calculated terms are divided into prediction period of2010,and expectation periods of2030and2050.This research can provide fundamental basis for the implementation of development strategies of the West.