Abstract: A new model for liquid membrane mass transfer is developed. This model takes into account botb the permeation process of solute through the inner core of emulsion globule and the effect of interf acial resistance enhancement caused by surfactant, thus providing reasonably accurate predictions for the mass transfer process in a liquid membrane system. Another feature of the present model is that the factor of membrane leakage isincluded in the model descriptions. This suits the mode] further to the practical conditions of the system. Both experimental results and theoretical analysis show that molecular diffusion through the very thin liquid layer of surfactant existing at the interface between emulsion globules and the continuous phase is the rate-controlling step for mass transfer in a liquid surfactant membrane system. This conclusion will lead to a deeper understanding of the membrane structure and will be helpful for improving membrane systems.