Based on the runoff drought index, the spring wheat yield data of Jiuquan, Zhangye and Wuwei in Hexi area, the relationship between the grades of runoff drought index and spring wheat yield without natural growth tendency is studied. The result shows that runoff drought index and spring wheat climate output of Hexi irrigational area appears opposite variation tendency. So, the change tendency of runoff drought index can be used to predict the variation tendency of output of spring wheat of this area.