The　SnO2/WO3　double　layer　thin　film　was　prepared　by　magnetron　sputtering　in　which　a　tin　(Sn)　target　and　a　tungsten　(W)　target　were　operated　in　radio　frequency　(RF)　reactive　mode.　The　crystallographic　structure　of　the　composite　was　investigated　by　X-ray　diffraction(XRD)　and　X-ray　photoelectron　spectroscopy　(XPS).　Results　reveals　that　the　SnWO4　is　formed　by　SnO2　and　WO3.　The　sensor　using　the　SnO2/WO3　double　layer　thin　film　was　prepared,　the　preparation　technology　parameter,　operated　condition　and　the　gas-sensing　properties　of　the　SnO2/WO3　double　layer　thin　film　sensor,　such　as　sensitivity,　selectivity,　response　and　recovery,　were　researched.　The　results　indicate　that　the　sensor　has　the　good　sensitivity　to　NO2　gas,　and　is　insensitive　to　other　disturbance　gases.