Abstract: In this paper, dehydration experiment of moist air simulated by air containing water with BmimAc ionic liquid as absorbent was carried out in the packed tower, packed with dixon gauze ring packing. The influences of ionic liquid flow rate, lean ionic liquid water content, liquid temperature, air flow rate and inlet moisture mass concentration on the dehydration effect were investigated. The optimum experimental conditions were achieved. The experimental results showed that the water dew point depression increased with the increasing of liquid flow rate and inlet moisture mass concentration, and decreased with the increasing of liquid water content, liquid temperature and air flow rate. Under the optimal conditions: ionic liquid flow rate 9 L/h, air flow rate 1 m³/h, lean solution water mass fraction 1%, inlet moisture mass concentration 18.26 g/m³, temperature 20 ℃, air dew point depression can be up to 40 ℃, water dew point of dry gas could be below -20 ℃ or less. In the field of industrial gases dehydration, indoor air drying and other fields, it had shown good prospects for application.