Abstract: To reveal the distribution of local flash flood disasters in arid areas, and discuss its forecasting methods, the authors analyzed the characteristics of flash flood disaster and constructed disaster risk evaluation model of the Shiyang River Basin by using its precipitation, flash flood disasters and disaster situation data. The results showed that: the flash flood disaster presented an increasing trend, and its high risk areas were mainly distributed in the Qilian Mountains line and the Wushaoling’s north and south sides in the upstream, the risks from Tianzhu upstream to Minqin downstream gradually reduced; flash flood mainly concentrated in April-September, and that in July accounted for 42.6% of the total number of occurrences; the occurrence time of flash flood and heavy precipitation was consistent; the ecological fragile Liangzhou was the most serious disaster region. Good forecast effect could be achieved by using NCEP/NCAR reanalysis data, conventional elements and the climate monitoring index, with stepwise decreasing FAR and the optimal subset regression method to forecast precipitation and flash flood trend from short-term, medium and long-term precipitation trends and heavy rain date.