Abstract: Coupled heat and water transfer in unsaturated soil was studied both theoretically and experimentally. Based on analyzing the mechanism of heat and water transfer in unsaturated soil, and the conservation principles of mass and energy, the theoretical model of heat and water migration in unsaturated soil was established. Numerical simulation was carried out for one dimensional heat and water migration by air convection. Experimental investigation of heat and water transfer of sandy soil with air convection was done. The temperature, volumetric water content and water table evaporation strength in varied air convection velocity were obtained by means of numerical simulation and experimental measurement.