The SWAP (Soil-Water-Atmosphere-Plant) model is an agro-hydrological model that is widely used in the fields of irrigation and water conservancy and soil science. It has developed rapidly in recent years. The SWAP model is used for formulation and evaluation of crop irrigation system, prediction of groundwater table depth dynamic, prediction of soil solute (salt, chemical fertilizer and pesticide) transport and prediction of crop growth and yield. This study briefly introducs the SWAP model and its theory. It summarizs the SWAP model that is simulated in soil water and salt transport, groundwater table depth dynamic, farmland drainage and crop growth and water productivity on the farmland scale. The SWAP model is also coupled with other models and could be extended from farmland scale to regional scale,for the sake of its better application and promotion. Morever, it points out that several problems and suggestings are worth attentions in the application of the SWAP model in order to make the model become more perfect.