In　this　paper,　flat-sheet　microfiltration　membranes　were　prepared　from　modified　polyvinyl　chloride-vinyl　acetate　(VC-co-VAc)　material　with　hydroxyl　group,　VC-co-VAc-OH,　by　phase　inversion　technique.　The　influences　of　casting　solution　composition　(polymer　concentration,　additive　types,　and　content)　and　preparation　conditions　(coagulation　temperature,　evaporation　time　of　solvent,　and　the　relative　humidity　in　the　environment)　on　pure　water　flux,　retention,　and　pore　size　distribution　were　discussed.　The　results　showed　that　casting　solution　composition　and　the　membrane　preparation　conditions　all　have　significant　impacts　on　the　performances　of　the　membrane:　on　the　one　hand,　in　order　to　prepare　membranes　with　high　flux,　either　decrease　the　polymer　concentration,　or　increase　the　PEG　molecular　weight　or　the　coagulation　temperature　or　the　relative　humidity　can　achieve　it;　on　the　other　hand,　with　the　increase　of　additive　content,　the　pure　water　flux　increased　quickly,　then　decreased　dramatically,　while　the　effect　of　evaporation　time　were　the　opposite.　And　these　results　were　confirmed　by　the　SEM　images.　Furthermore,　the　microfiltration　membranes,　which　were　prepared　under　optimized　conditions,　were　used　to　treat　synthetic　oilfield　polymer-flooding　wastewater,　and　good　experimental　results　were　obtained.