The objective of this research is to evaluate the risk of irrigation water requirement under climate change for an agricultural area in north Taiwan. On a basis of the result by last year (Huang, 2012. 101AS-8.2.5-IE-b1),the agricultural demand will be determined.Then the meteorological, hydrological and topographic fetures at Shihmen basin are investigated to construct a rainfall-runoff model. Finally, the simulation method is selected for evaluating the risk of irrigation water requirement under climate change. These results would be a well sugestion for decision-makers, and they could draw countermeasures by this research.