Acrylic　acid　(AA)　and　sodium　styrene　sulfonate　(SSS)　were　grafted　onto　poly　(ethylene-co-tetrafluoroethylene)　(ETFE)　film　by　pre-irradiation　technique　using　electronic　beam　from　a　2　MeV　accelerator　at　room　temperature.　A　humidity　sensing　film　with　strong　acid　and　weak　acid　groups　was　prepared.　Infrared　spectroscopy　analysis　of　the　grafted　film　confirmed　the　existence　of　sulfonate　and　carboxylic　acid　groups　in　the　grafted　film.　Thermal　and　chemical　properties　of　the　grafted　films　were　investigated.　The　crystallinity　and　static　contact　angle　of　the　grafted　films　decrease,　meanwhile　the　hydrophilicity　of　the　grafted　films　increases　with　increasing　grafting　yield.　A　resistive-type　humidity　sensor　was　prepared　using　the　grafted　film,　and　its　electrical　response　to　humidity　was　examined.　The　resistive　of　the　sensor　changes　linearly　by　4　orders　of　magnitude　over　almost　whole　humidity　range　(5%-98%　RH).　Furthermore,　the　sensor　exhibits　a　quick　response　(absorption:　less　than　1　min;　desorption:　less　than　2　min)　and　small　hysteresis　(less　than　2%　RH).