Due　to　the　hydrophobicity　of　poly(vinyl　chloride)　(PVC),　the　application　of　PVC　membranes　has　been　limited.　In　this　paper,　poly(vinyl　butyral)　(PVB)　was　introduced　as　the　second　polymer　component　to　hydrophilized　PVC　ultrafiltration　membranes.　The　miscibility　of　PVC/PVB　blends　in　N,N-dimethyl　acetamide　were　characterized　by　the　solubility　parameter,　glass　transition　temperature　of　the　blended　membrane,　casting　solution　viscosity,　etc.　The　results　showed　that　the　PVC/PVB　blended　system　was　partially　miscible　at　a　certain　proportion　range.　Water　flux　and　hydrophilicity　of　the　blended　membranes　were　much　better　than　that　of　the　membranes　made　from　pure　PVC　or　PVB.　A　cross　section　of　pure　PVB　and　PVC/PVB　blended　membranes　present　an　asymmetric　finger-like　structure,　and　the　wall　of　the　finger-like　pore　had　a　sponge-like　structure.　The　addition　of　PVB　could　improve　the　hydrophilic　property　of　PVC　membranes,　and　the　addition　of　PVC　could　increase　the　pore　diameter　at　the　bottom　of　PVB　membranes.