Abstract: Experimental research are conducted on heat transfer characteristics of WK400 air cooler under the constant condition of chilled water inlet temperature of 3 ℃ and outlet temperature of 19 ℃. The results show that the refrigerating capacity of air cooler increases with inlet air temperature and inlet air relative humidity and air quantity, and increases gradually quickly after the relative humidity higher than 50%, and increases gradually smaller after the air quantity more than 27 000 m³/h. The temperature increases with the higher of inlet air temperature and decreases with the increase of inlet air relative humidity and the air quantity, and decreases quickly after the air quantity more than 27 000 m³/h.