Abstract: Pervaporation(PV) or vapor permeation(VP) process was proved to be effective for removing the pollutant from industrial emission, dehydrating organic solvent and separating organic/organic mixtures.Depending on the feed state, researchers generally classify such processes as different membrane separation processes, and engineers design the separation with different method in commercial application. However, both pervaporation and vapor permeation can be analyzed based on the solution-diffusion mechanism, and they ought to possess identical permeation behavior.As a matter of fact, if observation was based on the viewpoint inside a polymer matrix, diffusion behavior of molecules in both operations would take on the identical nature.In order to obtain direct experimental evidence, a specifically designed equipment was developed.A stainless steel cylinder was connected with PV and VP membrane cells on both ends, and half of tank was filled with permeation feed. The feed in this tank showed vapor-liquid equilibrium, nitrogen sweep gas was introduced into the permeation side to remove the permeate on time. Therefore, pervaporation and vapor permeation processes were carried out in one tank simultaneously. This study used ethanol and 2-propanol aqueous, PVA/PAN composite membrane was used to measure individual component permeation behavior in PV and VP,and the results were analyzed based on the thermodynamic equilibrium theory. This investigation showed that water, ethanol and 2-propanol had the almost same permeation rate in both PV and VP process.The experimental results gave a direct evidence for the permeation behaviors consistency in a polymeric homogenous dense membrane.