Abstract: Based on the stability theory of microemulsions, a title model has been established. Key factors considered are the association of surfactant molecules on the oil-water interface, extra energy caused by the bending of the surface membrane, and various entropies of mixing. Electrostatic interactions are also taken into account because of the charge characteristics of surfactant and protein molecules. The model presented can properly describe the size change of reverse micelles after the protein uptake. The experimental results of the protein transfer ratio as a function of salt concentrations can also be reproduced satisfactorily.