| Soil water balance of CERES-Wheat was assessed for Zhengzhou of Henan province. Based on validation of water balance, daily weather data of 16 stations in Henan to model irrigation requirement of crop during 1961—2009, and temporal and spatial characteristics of irrigation requirement of crop were analyzed. Irrigation requirement at every stage was compared between the northern and the southern regions in Henan. The results showed: (1) the irrigation requirement of crops in the northern regions was more than that in the southern regions in Henan, with irrigation amounts being 307～499 mm for dry years，256～432 mm for normal years, and 169～372 mm for wet years; (2) irrigation requirement of crops showed decreasing trend in most of the eastern region. Significant correlation between irrigation requirement and evapotranspiration existed; (3) The irrigation requirements reached the highest level in the apical spikelet formation and mature period; in some year with less precipitation, the winter wheat in the southern regions is similar to in the northern regions. Even for years with more precipitation, irrigation requirement was necessary at the stage apical spikelet formation. |