PDMS-b-PPO　copolymers　are　synthesized　by　hydroxyl-amine　condensation　reaction,　and　applied　in　the　separation　of　ethanol/water　binary　mixture　by　pervaporation.　The　reaction　between　aminopropyl-terminated　PDMS　and　hydroxyl-terminated　PPO　are　conducted　for　more　than　10　h　with　the　existence　of　dilute　H2SO4　at　120　°C.　White　powder-like　block　copolymers　are　obtained,　and　the　structures　are　characterized　by　1H-NMR.　Results　show　that　the　configurations　of　product　are　predicted　to　be　AB　and　ABA　types.　Through　solvent　evaporation,　the　homogenous　membranes　are　prepared,　and　results　show　that　the　membranes　are　ethanol　perm-selective,　compared　with　PDMS　membranes,　the　separation　performance　and　mechanical　properties　are　improved.