The present work is proposed to evaluate the potential of using pervaporation process to separate water-acetic acid mixtures. A composite membrane of. polyacrylic acid (PAA) dip-coated asymmetric poly(4-methyl-1-pentene) (TPX) membrane was prepared. To improve the interface peeling of the PAA/TPX composite membrane, the TPX membranes were surface-modified with residual air plasma in a tubular-type reactor. The surface properties of the plasma pretreated TPX membrane was characterized by atomic force microscopy (AFM) and water contact angle meter. The PAA/TPX composite membrane with plasma pretreatment effectively prevents the interface peeling. The effects of feed concentration, substrate membrane structure, plasma treatment conditions and compositions of coating solution on the pervaporation performances were investigated. Optimal results were obtained With the PAA/TPX composite membrane prepared from the PAA/ethylene glycol (EG)/aluminum nitrate = 1/2/0.05 coating solution at the 5W/30s plasma treatment condition. The water concentration of the permeate approach to 100wt.% and a 960 g/m(2) h permeation rate with a 3wt.% feed acetic acid concentration at 25degreesC was obtained.