The PVA/P(AA-Co-AN)/PVA composite membrane was prepared to separate methanol from aqueous solution. Acrylic acid (AA) and acrylonitrile (AN) were synthesized by solution polymerization with nanometer SiO2. The copolymer solution P(AA-Co-AN) was made into main body of the membrane, with the polyvinyl alcohol (PVA) acetal membrane on both sides, to make the composite pervaporation membrane. The swelling behavior of membrane in methanol dense aqueous solution was explored. The effect of dipping temperature and concentration on the swelling degrees was also measured. Mechanical property of the membrane was investigated by stretching test. The performances of the membranes prepared with different n(AA):n(AN) ratio were investigated through pervaporation experiments at different temperatures and different feed composition. The results of swelling and pervaporation experiments show the membrane has an encouraging swelling and pervaporation behavior in methanol dense aqueous solution. The membrane prepared with n(AA):n(AN)=1:1 gave the highest separation factor of 1534 and a permeation flux of 583 g/(m2•h) at 60℃ in pervaporation of w(methanol)=98% aqueous solution.