Abstract: A permeation swelling model for W/O/W multiple emulsions was developed. Both the osmotic pressure difference between the internal and the external phases and the changes of permeation area with time were considered to obtain the analytic solutions. The model predictions were in good agreement with the experimental data. The experimental results indicate that apart from the osmotic pressure gradients, the membrane compositions such as the membrane solvents, the surfactants and the carriers also influenced the swelling. The effect of the oxygen-containing compounds on the swelling was larger than that of the nitrogen-containing compounds.