Organic　solvent　nanofiltration　is　a　promising　separation　technology　for　removing　solute　from　an　organic　medium.　However,　the　fabrication　of　organic　solvent　nanofiltration　membranes　with　stable　separation　performance　is　still　a　challenge.　Herein,　a　hydrophobic　polyelectrolyte　multilayer　membrane　was　prepared　through　a　layer-bylayer　self-assembly　and　counterion　exchange　method.　Poly(diallyl　dimethyl　ammonium　chloride)　(PDDA)/polyacrylic　acid　(PAA)　multilayer　was　self-assembled　on　the　surface　of　the　hydrolyzed　polyacrylonitrile　substrate　through　electrostatic　interaction.　Simultaneously,　calcium　silicate　hydrate　(CSH)　nanoparticles　were　in　situ　grown　during　the　multilayer　formation　process　due　to　the　incorporation　of　precursor　in　polyelectrolyte　solutions.　Therefore,　the　surface　roughness　of　the　membrane　was　enhanced　and　the　anti-swelling　property　of　the　polyelectrolyte　multilayer　was　also　improved.　The　hydrophilic　[(PDDA/PAA-CSH)(2.5)]Cl-+(-)　membrane　was　then　converted　to　the　hydrophobic　membrane　through　the　counterion　exchange　between　Cl-　and　perfluomoctanate　(PFO-)　ions.　The　obtained　[(PDDA/PAA-CSH)(2.5)]+PFO-　membrane　has　a　water　contact　angle　of　118　degrees,　which　can　be　used　to　separate　dyes　from　ethanol.　Both　the　separation　performance　and　stability　of　the　polyelectrolyte　multilayer　membrane　were　improved　through　the　in　situ　growth　of　calcium　silicate　hydrate　nanoparticles　and　counterion　exchange　by　perfluomoctanate　ions.　Therefore,　this　strategy　may　open　a　new　avenue　to　prepare　organic　solvent　nanofiltration　membranes.