The　chemical　modification　method　was　used　to　improve　the　hydrophilicity　of　polyvinyl　chloride-vinyl　acetate　copolymer　(VC-co-VAc).　The　experimental　results　showed　that　the　polymer　material　VC-co-VAc-OH　can　be　obtained　by　hydroxy　modification　from　VC-co-VAc.　Then　the　polymer　of　VC-co-VAc-OH　was　used　to　prepare　asymmetric　flat-sheet　membranes　with　the　solvent　of　dimethyl　acetamide　(DMAc)　and　the　additive　of　polyethylene　glycol　20000　(PEG　20000)　by　using　phase　inversion　technique.　When　the　polymer　concentration　was　16　wt.%,　mass　ratio　of　solvent　to　additive　was　10:　1,　coagulation　temperature　was　20　degrees　C,　evaporation　time　was　30　s　and　relative　humidity　was　50　%,　a　membrane　with　good　performance　could　be　prepared.　These　results　were　supported　by　experimental　data　of　pure　water　flux,　retention,　water　content　and　pore　size　distribution.　(C)　2011　Published　by　Elsevier　Ltd.　Selection　and　peer-review　under　responsibility　of　RIUDS