Abstract: Based on the equations of energy and moisture balances, radiation transfer and thermodynamics, a 2-dimensional land-air dynamic model with vegetation effect in the entity of soil-vegetation-atmosphere is developed. Variations of heat and moisture with height and latitude are modeled. Taking account of geographic and climate features, the climatic mean fields over the northern part of Shaanxi Province are simulated with the model, thereby the simulation scheme for understanding desertification over the semiarid is presented and the preliminary computational results are obtained.