A　novel　nanocomposite　thin　film　material　of　SnO2/WO3　metal　oxide　compound　doped　by　multi-walled　carbon　nanotubes　(MWCNT)　and　its　corresponding　gas　sensor　were　prepared　by　radio　frequency　(RF)　reactive　magnetron　sputtering.　The　surface　composition　and　chemical　elements　of　the　thin　film　material　were　respectively　analyzed　and　validated　by　X-ray　diffraction　(XRD)　and　photoelectron　spectroscopy　(X　PS).　The　influencing　factors　of　gas　sensing　properties　were　studied　and　the　test　results　of　gas　sensor　were　analyzed.　The　results　indicated　that　the　detection　using　the　composite　material　gas　sensors　for　low　concentration　NO2　toxic　gas　could　be　greatly　improved　by　MWCNTs　which　were　doped　on　the　mixed　oxides　matrix.　A　possible　mechanism　explaining　the　behaviour　of　the　thin　film　gas　sensor　was　introduced.