The Typical Meteorological Day of Guangzhou summer was realized in Hot-Wet Climatic Wind Tunnel, and the thermal transfer process of two specimens with the same construction was studied in the wind tunnel.In the experiment process, one of the specimens was watered and the other one was not watered.The experiment result illustrated that the evaporative cooling effect was very significant when the specimen was watered.Compared with the non-watered specimen, the highest outer surface temperature and the highest inner surface heat flux of the watered specimen decreased by 10.9 ℃ and 14.8 W/m2, respectively.Additionally, the thermal resistance of the watered specimen was one time bigger than that of the non-watered specimen.It was demonstrated that the watered specimen had better heat-insulating property than the non-watered specimen.Moreover, the Penman-Menteith model was used to calculate the hourly evaporation of the watered specimen.The total hourly evaporation was divided to thermal evaporation and dynamic evaporation.The variations of the total hourly evaporation, thermal evaporation and dynamic evaporation were analyzed.The hourly evaporation data were used to calculate the surface thermal balance equation.The result illustrated that 64.5% incoming short wave radiation was consumed in the evaporating process.In summer, evaporating process could decrease the solar radiation illuminated on the building surface, diminish the surface temperature, reduce the thermal flux flowing into the room and save the air-conditioning energy consumption.