ABSTRACT: Characteristics change and differences of polydimethylsiloxane (PDMS) and polymethylvinyl- siloxane (PVMS) membrane before and after extraction were investigated by measuring swelling property and surface performance. The results showed that the swelling degree and the contact angle of PVMS were higher than that of PDMS, indicating excellent hydrophobicity. Chemical structure of membrane changed after treatment. PVMS had better ability of perstraction for organic component than PDMS. Therefore, simple device equipment with PVMS was employed to remove the pentanoic acid from an aqueous solution, and the effects of the influent concentration, influent flow rate, and extraction solvent on permeation extraction were discussed. At the same time, the possible separation mechanism of this process was analyzed. It was found that with the increase of influent concentration, the removal extent and recovery of the pentanoic acid increased but decreased later. The removal extent of PVMS membrane reached 94% at concentration of 7%, and recovery extent reached 45.8% at concentration of 2%. Removal extent with the alkali solution was higher than that with the water in receptor liquor. And receptor liquor with sodium carbonate had better applicability. The removal and recovery extent can be improved by increasing the flow rate between 1 and 20 milliliters per minute, which can enhance separation effect in the practical application.