Abstract: Effect of regulated deficit irrigation (RDI) conducted in seeding stage of maize on the physiological status and water requirement was studied in the paper based on field experiment in Huoquan Irrigation District, Shanxi Province during 2 growing seasons. The results indicated that RDI could postpone leaf senescence and increase photosynthesis rate, transpiration rate and root activity in later stage. Photosynthesis rate and transpiration rate were lower than those of control treatment after recovering of water in jointing and heading stage,but higher in filling stage. Water consumption in seeding stage, jointing stage and heading stage under RDI were less than those of the control treatment but more in filling stage. Total water requirements during the whole growing season under RDI were less.