Abstract: A water and nitrogen management model(WNMM) was used to simulate the soil water and nitrogen dynamics in fluvo-aquic soil,with a view to establishing a scheme to optimize soil water and nitrogen in light of local climate and soil properties.The model was validated by field experiments in fluvo-aquic soil.Results show that the model did good in simulating water and nitrogen dynamic.The simulated values of evaportranspiration,soil water and nitrate content displayed significant correlation(α=0.01) with measured values,and the deviation are acceptable.Based on real-time data of soil water and nitrogen content,an optimal irrigation and fertilization scheme was figured out.Under the average climate conditions of years,the scheme could not only provide a preferable soil environment for crop growth,but also save irrigation water by 163.5 mm and nitrogen fertilizer by 130 kg·hm^-2 and decrease soil water and nitrogen leaching by 264.6 mm and 71.1 kg·hm^-2,respectively,each year.