Abstract: The modified form of wetted-wall column developed by Hikita et al. was used, for studying gas-liquid mass transfer. The thickness of liquid-film along the surface of the wall was measured. The experimental results agreed quite well with the theoretical values. By measuring characteristics of mass transfer of liquid-film with CO2-H2O System an equation of dimensionless groups for liquid-film mass transfer coefficients has been proposed. The experimental results agreed well with theoretical values according to penetration theoy. The study has also shownd that the deviation caused by the end-effect be eliminated by simple operational control. Thus, the modified wetted-wall column is a good equipment for studying gas-liquid mass transfer.