Lysozyme was extracted from aqueous solution into i-octane using reverse micelles in the presence of pressurized CO2. A squat vessel with two independent stirrers was used to measure the mass transfer of the lysozyme across a planar interface. Mass transfer coefficient, k(L) of the lysozyme from the aqueous to the organic phase was measured at selected ionic strengths, pH, sodium bis(2-ethylhexyl) sulfosuccinate (AOT) surfactant concentrations, temperatures and pressurized CO2. The mass transfer rate of lysozyme was higher in high temperature (318 K) and pressure (20MPa). pH of 9 in aqueous phase showed highest mass transfer rate of lysozyme. The application of pressurized CO2 markedly increased the mass transfer rate of lysozyme comparing to conventional non-pressurized system.