Based on meteorological data from China national weather stations and climate scenario grid data through regional climate model provided by National Climate Center,rice water requirement was calculated by using McCloud model and Penman-Monteith model combined with crop coefficient approach. Then the rice irrigation water requirement was estimated by water balance model,and the changes of rice water requirement were analyzed. The results indicated that either in historical period or in climate scenario,rice irrigation water requirement contour lines during the whole growth period and L_(mid) period decreased along southwest to northeast,and the same irrigation water requirement contour line moved north with decade alternation. Rice irrigation water requirement during the whole growth period increased fluctuantly with decade alternation at 44. 2 mm?10 a~(-1) in historical period and 19. 9 mm?10 a~(-1) in climate scenario. The increase in rice irrigation water requirement during the L_(mid) period with decade alternation was significant in historical period,but not significant in climate scenario. Contribution rate of climate change to rice irrigation water requirement would be fluctuantly increased with decade alternation in climate scenario. Compared with 1970s,contribution rates of climate change to rice irrigation water requirement were 23. 6% in 2000s and 34. 4% in 2040s,which increased 14. 8*10~8 m~3 irrigation water in 2000s and would increase 21. 2*10~8 m~3 irrigation water in 2040s.