Dual　sensitive　sensor　is　a　new　type　of　sensor.　During　the　research,　the　stability　of　sensor　is　a　difficult　problem　need　to　be　solved　urgently.　The　Nb2O5　material　was　doped　to　the　original　sensitive　material　and　the　material　was　made　into　sensor.　Then,　two　year＇s　tracking　test　was　carried　on　to　the　properties　of　the　sensor.　Result　shows　that　the　stability　of　sensor　is　good.　The　microstructure　of　sensitive　material　was　detected　by　XRD,　SEM　and　TEM.　The　results　of　analysis　show　that　the　doped　material　after　sintered　form　into　solid　solution　and　the　partial　solid　solution　material.　The　solid　solution　state　of　material　made　the　properties　of　gas　and　humidity　maintaining　at　the　steady　state.