The dehydration of moist air using ionic liquids (ILs) in a rotating packed bed (RPB) was innovatively studied. The effects of operating conditions, including rotational speed, liquid and gas flow rate, temperature, inlet gas water content, and water content of lean solution on the water dew point depression (Delta T-d) in the RPB, were systematically studied. The experimental results showed that the water dew point depression can be up to 40 degrees C under the optimum experimental conditions of a motor speed of 1695 rpm, a liquid gas ratio of 9 L/m(3), temperature of 20 degrees C, lean solution water content of 0.8 wt %, and inlet gas water content of 18.77 g/m(3). Moreover, a correlation to predict the water dew point depression was established, and the data predicted by the correlation is consistent with the data of experiment, with deviations of +/- 10%. This work exhibits great potential application of ILs in gas dehydration process in a RPB.