Abstract: In this paper,based on the risk analysis theory,a risk assessment model for agricultural drought is developed,which includes the occurrence probability of drought,capacity of drought prevention,percentage of planting area,etc.The relative yield is introduced as the agricultural drought index reflecting the impaction of water transport in the SPAC system on the yield.By means of the index and the model,the agricultural drought risk of irrigation area is evaluated,which analyses the living phase of crops with the highest influence on risk degree of crops and the crop of the most risk degree.The results would greatly benefit to establish reasonable scheme of drought prevention and alleviate the disaster loss.