Dunhuang Airport in Gansu is an important transportation hub located in the northwest of China. The airport terminal is a spacious building with a large population flow and T3 terminal has recently been completed. It has the combined characteristics of lower outdoor wet-bulb temperature, a higher diurnal temperature range and abundant dry air energy in local summer air. In the design of the air conditioning system, a combination of evaporative cooling and traditional mechanical refrigeration is adopted to be a composite cooling system where the ability to switch operating methods allows a greatly reduced working time of mechanical refrigeration whilst simultaneously achieving the air conditioning function to meet the passengers’ demands of fresh air volume and reducing initial investment and operating cost of the air conditioning system. This research involved testing the indoor supply-air parameters and environment comfort of the evaporative water chiller installed in the refrigeration station and the terminal. It was found that the supply-water temperature is 0.5°C higher than the ambient wet-bulb temperature, and the efficiency of the evaporative water chiller was 97.3%., indicating that the system can achieve a great economic and energy-saving effect. Meanwhile, the combination of these two cooling technologies provides a new direction for the design of air conditioning systems in dry areas. Finally, we analysed the possible reason for the phenomenon that the supply-water temperature is not below the wet-bulb temperature of ambient air and there might be scaling, air duct obstruction and operation mode problems in the system.