A diffusion model is developed to simulated the behavior of mass transport of the solute in the emulsion liquid membrane. The solute is allowed to react reversiblely with the internal reagent, and the effective diffusivity of the solute in membrane phase is dependent on local solute concentration in membrane phase. A numerical solution is presented for the non-linear equations of this model. The results are compared with those of two previous models, and it is found that the Modified Diffusion Model represents more accurately than other earlier models.