Abstract: The equilibrium solubility of alcohol and water in two polyimide membranes measured in a previous work is correlated by the dual - mode theory with Flory-Huggins solution model and Langmuir adsorption model. Diffusion coefficient - concentration relations are evaluated from experimental sorption and desorption curves. Solubility coefficients, permeabilities are then obtained. The infinite dilution ideal separation factor is used for the appraisal of separation performance of pervaporation membrane. It is shown that the diffusion coefficients and permeabilities of alcohol and water in the membrane containing crosslinking agent are less than in that without crosslinking agent. However, the infinite dilution ideal separation factors in the former are larger than that in the latter. The results indicate that the crosslinking agent can improve the performance of polyimide membrane for the separation of alcohol and water.