Abstract: Field irrigation management and model establishment are always a core and difficult content in crop simulation. The research focused on exerting the establishment theory of knowledge model, and applying the systematic analysis method and mathematic modeling technology to knowledge expression system of maize water management, based on soil water balance, a dynamic knowledge model with systematic and wide-application characteristics for maize water management was developed, after quantifying the relationship of irrigation to cultivars' characteristics and environmental factors periodically. Cases were studied on the knowledge model with the data sets of normal year in different eco-sites and those of different rainfall years in the same eco-site. The results show that there is no difference on saving water in normal year under different eco-sites, irrigation ration changes with eco-sites(Table 3); more difference in different rainfall years of the same eco-site, which is 8.6% in more rainfall year and 31.9% in normal rainfall year(Table 4), and irrigation in seeding does not change with year, but in Knurling and Filling they do. Irrigation system designed by the model is coherent to the actual planting system well. This indicates that the model has good decision-making ability and applicability.