Abstract: Abstract: The agricultural water and ecological water have been continuously squeezed due to increasing urban domestic water consumption in China. Moreover, the inconsistency between water supply and demand in agriculture has been threating the regional food security, ecological environment protection, and social stability. Therefore, the study on crop water requirement and water-saving irrigation mode is important to mitigate the water shortage in agriculture. In this paper, yield and water demand regulation of paddy rice under different irrigation modes were analyzed based on the field experiments conducted in 2009-2013 at Changqu Irrigation Station (31°11′N, 112°11′E), Xiangyang, Hubei Province. ORYZA_V3 model was calibrated against the measured rice yield obtained in 2010, and validated with measured rice yield obtained in 2011. Then, the calibrated model was used to simulate the rice growth for 30 years (1981-2010) under three traditional irrigation modes and several drought schemes, which were designed with combinations of lower limits of irrigation, irrigation water quotas, and irrigation times for drought in different rice growing stages. Based on model outputs, evapotranspiration and water consumption were calculated for each growing stage,and irrigation quota, irrigation times, yields and water productivity were compared. Based on that, an optimum irrigation mode was proposed for this region, and its water-saving potential was calculated. The results indicated that, compared to shallow irrigation (SI) mode, the annual average yield under wetting irrigation (WI) mode increased by 2.7% and the irrigation quota decreased by 4.2%, whereas the yield under middle-store irrigation (MI) mode decreased by 2.3% and the irrigation quota decreased by 1.1%. Thus, among the traditional irrigation modes, WI mode is better than SI mode and MI mode from the points of saving water and improving production. Furthermore, lower irrigation threshold less than 90% of saturated soil moisture in tillering stage (TL) reduced evapotranspiration by more than 47%, and in other stages evapotranspiration were reduced by more than 10% when the irrigation threshold was less than 70% of saturated soil moisture. In addition, drought in jointing-booting (JB) and heading flowering (HF) stage had stronger effects on rice yield than that in other stages. After an overall consideration of water-saving, field management efficiency and food security, the optimum irrigation mode for this region was suggested: The maximum water level in field after rain was set as 60 mm, thin water layer should be kept in returning green (RG) and heading flowering (HF) stages, whereas natural fall was advisable in yellow-ripping (YR) stage, and moderate drought was allowed only in jointing-booting (JB) and milky-ripening (MK) stages with lower limit of irrigation between 70%-80% of saturated soil moisture while light drought was suggested in other stages with the lower limit of irrigation higher than 80% of saturated soil moisture, and the irrigation water quota was set as 30-40 mm. The optimum irrigation mode had great water-saving potential, which could save at least 0.168 billion m3 water for northern part of Hubei Province. The results of this study were of important significance in guiding the irrigation for paddy rice in this region.