Separation of protein by using colloidal gas aphrons (CGAs) is a promising method for removing organic materials from an aqueous solution. In this study, the continuous separation of lysozyme was carried out in a flotation column by using a CGA. The mechanism of adsorption of lysozyme on the CGA and the mass transfer from lysozyme to CGA were investigated. It was found that the adsorption of lysozyme on the CGA followed the Langmuir adsorption isotherm at a lysozyme volumetric flow rate of 2.37 mL/s. In the study of mass transfer, the overall mass transfer coefficient increased with the lysozyme and CGA volumetric flow rates, but decreased with increasing column height. The percentage of protein recovery increased with the lysozyme and CGA volumetric flow rates, column height, and residence time.