In this article, the composite polydimethylsiloxane (PDMS) membranes supported by cellulose-acetate (CA) microfiltration membrane were successfully prepared by adding nano-fumed silica particles modified with a silane coupling reagent, NH2-C3H6-Si(OC2H5)3. The effects of silica content, feed concentration, and feed temperature on the pervaporation performances of the nano-composite PDMS membranes were investigated for recovering ethanol from aqueous solution by pervaporation. It was found that adding the modified silica particles significantly improved the pervaporation performances of the composite membranes. When the silica content in the membrane was 5wt%, for a 5wt% ethanol/water mixture at 40 degrees C, the permeation flux of the membrane maintained about 200g center dot m-2 center dot h-1 and separation factor reached the maximum value of 19.