We present a numerical method to simulate the permeation behavior of oil–in–water (O/W) emulsions with soluble surfactants through a membrane pore. Our numerical frame work is based on the phase–field model, which enables us to capture the thermodynamic and hydrodynamic effects of surfactants on oil droplet motion. We investigated the effects of surfactant concentration on the permeation behavior of oil droplets. Existence of surfactants made demulsification behavior complicated because oil droplets covered with surfactants are deformed easily by permeation flow.