Abstract: A simulation model of nitrogen behavior and cycling in soil-plant systems was discussed. This model was developed based on the home and foreign successful models of nitrogen behavior in soil-plant systems, and amended and repackaged for fitting in with the local specific conditions. Some processes of nitrogen were included such as mineralization/immobilization, denitrification, nitrate loss in surface runoff, and nitrate leaching in this model. It was validated by using the results of field trials on winter wheat for three years. There was agreement within the measured and simulated values of grain dry weight, %N in the grain, nitrate and water in 0-90cm depth of soils, total biomass and %N in the above ground parts of plant. Research results indicated that the simulation model can be used to predicting the nitrogen behavior of calcareous soils in arid and semiarid area of china.