In the salt-fresh water region an optimization planting structure model is developed by combinning the groundwater control system with the cropping system. The object of this model is to maximize the net benifit of the crop production under the restrictions of water, soil resource, and so on. This model has been applied to determine the schemes of the planting structure optimization in Nanpi County for the years 1985, 1990, 1995, and 2000.