The soil moisture content plays the vital role in the interaction of land-gas and balance of energy-water of surface land. However, in recently, the one dimensional bucket pattern is used as many land surface process models to compute the soil moisture content, which neglects the problems that the lateral supplies, the groundwater level and the penetration coefficient are function to saturation. Therefore, this article, based on the saturated-unsaturated theory which is domestic and mature over world, proposed simulation method of coupling the package of soil moisture transmission model and the land surface process pattern, and expressed dynamically the soil moisture migration process and change of groundwater level change under unstable state. Using the established coupling model, taking the Hexi corridor-Heihe basin middle reaches as the example, this article also simulated changes on the soil moisture content and the groundwater level under condition of different irrigating during wheat growth period in arid inland region, the results indicated the model established in this article was allowed to calculate changes of the instant soil moisture content and the groundwater level, and estimate the water consumption during the wheat growth period, then provide an rational academic basement for the reasonable agricultural irrigation