Upon the simulation and estimation of the impact from climatic changes on net irrigation requirement quota of crop,irrigation water requirement (I_N) and total crop water demand (W_t) in Shiyang River Basin could provide support for efficient use of water resources and sustainable development of agriculture.While daily ET_0 and precipitation in 2020 s,2050 s and 2080 s were downscaled from HadCM3 (Hadley centre Coupled Model,version 3) outputs under A2 and B2 emission scenarios by SDSM (Statistical Downscaling Model),based on meteorological data from 11 meteorological stations located in and around the Shiyang River Basin during 19512012.Net irrigation requirement quota,I_N and W_t were calculated by using crop coefficient method,and removing the effective rainfall.The spatial distribution of net irrigation requirement quota was investigated by Inverse Distance Weighted Interpolation. The results showed that net irrigation requirement quota performed an increasing tendency from southwest to northeast gradient for wheat,maize,sweet pepper,cotton,sesame and apple.HadCM3 projected an increasing trend for these six typical crops.The present I_N and W_t were 12.65 * 10~8 m~3 and 15.42 * 10~8 m~3,respectively in the whole basin. When the present planting structure was maintained,under A2 emission scenario,the I_N were 13.45 * 10~8 m~3,15.02 * 10~8 m~3,and 16.94 * 10~8 m~3,and the W_t were 15.53 * 10~8 m~3,16.65 * 10~8 m~3,and 18.18 * 10~8 m~3,respec tively in 2020 s,2050 s and 2080 s.Under B2 emission scenario,the I_N were 13.55 * 10~8 m~3,14.63 * 10~8 m~3,and 15.51 * 10~8 m~3,and the W_t were 15.56 * 108 m~3,16.34 * 108 m~3,and 17.00 * 10~8 m~3 respectively in 2020 s,2050 s and 2080 s.A remarkable increasing temporal trend was observed in net irrigation water requirement,I_N and W_t. The increase under B2 scenario was lower than that under A2 scenario.There would be a significant increasing trend about requirement of irrigation water in the future,which would especially be more significant after the 2050 s.