The waterborne polyurethane membrane was synthesized with poly-1

4-butylene adipate glycol (PBA-2000) and toluene diisocyanate (TDI) and the properties of pervaporation benzene/cyclohexane mixture were tested to study the mass transfer characteristics during pervaporation process. From experimental data it can be concluded that the separation factor and flux should get bigger and smaller obviously as the membrane is very thin. And the variation of separation factor and flux was slight as the membrane thickness was certain thick. The improvement of downstream vacuum of the membrane should improve both the separation factor and flux. The bigger feed concentration and temperature should increase the flux and decrease the separation factor. The components in the pervaporation membrane should undergo the course of adsorbing swelling-evaporation in membrane-gaseous diffusion. The dry region of the membrane plays more effect during the pervaporation process.