Abstract: The kinetics of BSA extraction has been studied with CTAE-hexanol-octanereversed mice11ar solution.In order to determine the overall mass-transfer coefficients,astirred transfer cell with constant interface was operated under varied conditions,such as thestirring speed,the pH value and ionic strength in aqueous phase,and the concentration ofsurfactant and cosolvent.The results showed that the extraction is controlled together byinterfacial process and diffusion through the aqueous film.The individual mass transfer coefficients of diffusion in aqueous phase were calculated,so that a series of individual interfacialcoefficient at various aqueous phase conditions could be obtained.It shows that the interfacial transport of BSA occurs via a cooperative mechanism.The interfacial transfer rate isstrongly affected by the electrostatics in protein/interfacial interaction,which determines theextent of deformation at the interface.