Abstract: For exploring a rotational irrigation model with the salty and fresh water which fits the feature of the Hetao irrigation area in Inner Mongolia and affects the regional soil and underground water enviroment most lightly, with the prediction of the regional enviroment variety with long-term salty and fresh water irrigation, coupling model and algorithm described unsaturated-saturated soil water and salt movement is established, based on the field experiment and spatial structural zone by soil water and salt information. The verification of calibration results to the coupling model turns out that the values calculated by model and the measured actual fit well. Coupling model can make circulation calculation smoothly, with error below allowable range, as shows the great reliability of the coupling model. Numerical simulation study of irrigation model with the salty and fresh water, based on the coupling model, indicates that “fresh-salty-salty” Rotational Irrigation pattern minimizes the effect environmental impact to regional soil and underground water environment to other patterns. Adopting “fresh-salty-salty” pattern as long-term light salty water irrigation, the desalting amount in growth period is larger than that in non-fertile period. The salt mainly drains away the region via ditch system. The soil is desalting generally. The level of underground water declines little in the stimulating period. Salinity of underground water and salt in the aquifer are downtrend. With the reduction of the Yellow River water, “fresh-salty-salty” pattern provides a way to maintain the sustainable development of regional environment. The coupling model provides reference and simple practical way for the implement to the region where the water-saving improvement project is implement and the prediction of the regional water and soil environment with utilization of the brackish water.