The　layer-by-layer　(LbL)　assembly　of　polyelectrolyte　multilayers　on　to　a　porous　supporting　membrane　is　able　to　create　various　new　composite　membranes.　However,　the　low　efficiency　and　long　time　required　for　such　procedures　limit　practical　applications.　In　this　study,　an　automatic　spray　system　has　been　constructed　for　the　rapid　assembly　of　polyelectrolyte　multilayers　on　to　nanoporous　supporting　membranes.　The　compounds　polyacrylic　acid　and　poly(ethyleneimine),　used　as　a　model　polyelectrolyte　pair,　were　alternately　sprayed　on　to　a　polyacrylonitrile　ultrafiltration　membrane.　Experiments　proved　that　the　composite　membrane　obtained　in　this　way　had　a　good　pervaporation　dehydration　performance.　In　addition,　the　process　times　were　dramatically　decreased,　by　as　much　as　80　folds,　when　compared　with　classical　dip-LbL　methods.　Such　an　automated　system　can　easily　be　converted　to　the　assembly　of　various　organic　species.　Therefore,　it　is　a　versatile　and　highly　efficient　system　for　manufacturing　composite　multilayer　membranes　for　many　separation　applications.　(C)　2012　American　Institute　of　Chemical　Engineers　AIChE　J,　59:　250-257,　2013