Soil moisture and evaporation are important factors in process of hydrologic cycle and energy transformation. Considering the wet region with high groundwater table, the writer put forward an evaporation model in relation with soil moisture and flux of groundwater based on the fundamental principle of water movement in the unsaturated soil and water supply to the evaporation layer from groundwater. As there is a single function of soil suction in the model, the physical calculation is quite simple.