In terms of 38 Year′s(1959—1996) monthly runoff data of Changmabao,Yingluoxia and Jiutiaoling Hydrological station which represent three main inland rivers in Hexi area respectively,the anomalous percentage of runoff and its degree of high/low flow were analysed.The runoff drought index was specified by processing runoff normally and its grades of dryness/wetness was divided.Considering of the drought index grades and the situation of agriculture irrigating,some reasonable suggestions about irrigating were given.