As　polyacrylonitrile　(PAN)-based　membrane　plays　all　important　role　in　the　processes　of　pervaporation,　bioproduct　purification　and　water　treatment,　this　study　aims　at　better　understanding　the　hydrolysis　differences　by　using　different　alkaline　species,　and　how　the　hydrolysis　degree　affect　the　subsequent　modification　of　hydrolyzed　PAN　membranes.　The　ATR-FTIR　spectra　and　the　measurements　of　ion　exchange　capacity　(IEC)　demonstrated　the　differences　of　hydrolysis　degree　among　the　KOH,　NaOH　and　LiOH　hydrolyzed　PAN　membranes.　The　microtopographical　changes　on　membrane　surfaces　were　characterized　by　atomic　force　rnicroscopy.　It　was　found　that　the　membrane　surface　toughness　decreased　with　the　increase　in　the　hydrolysis　degree.　The　molecular　weight　cut-off　(MWCO)　of　the　hydrolyzed　membranes　was　determined　by　filtration　studies　using　poly(ethylene　glycol)　and　Cytochrome　C　solutions.　It　was　noted　that　the　MWCO　of　the　PAN　membranes　decreased　from　20,000　to　6000　after　hydrolysis　with　2　N　NaOH　or　2　N　KOH　for　I　h　at　65　degrees　C.　Subsequently,　the　polyethyleneimine　(PEI)　was　deposited　on　the　top　surface　of　the　hydrolyzed　PAN　membrane　to　form　a　composite　membrane.　The　pervaporation　performance　and　ions　rejection　property　of　the　PAN/PEI　composite　membrane　clearly　demonstrated　that　the　hydrolysis　difference　had　a　great　influence　oil　subsequent　modification　of　the　PAN-based　membrane.