NOx　is　one　of　dangerous　air　pollutants,　and　the　demands　for　reliable　sensors　to　detect　NOx　are　extremely　urgent　recently.　Conventional　fluorite-phase　YSZ　used　for　NOx　sensor　requires　higher　operating　temperature　to　obtain　desirable　oxygen　ion　conductivity.　In　this　work,　perovskite-phase　Na0.5Bi0.5TiO3　(NBT)　oxygen　conductor　was　chosen　as　the　solid　electrolyte　to　fabricate　a　novel　highly　sensitive　NO2　sensor　with　CuO　as　the　sensing　electrode　and　Pt　as　reference　electrode.　Na　dopped　Na0.5Bi0.5TiO3　greatly　improved　the　sensing　performance　of　this　sensor.　The　optimal　sensor　based　on　Na0.51Bi0.50TiO3-(delta)　exhibited　good　response-recovery　characteristics　to　NO2　and　the　response　current　values　were　almost　linear　to　NO2　concentrations　in　the　range　of　50-500　ppm　at　400-　600　degrees　C.　The　response　current　value　towards　NO2　reached　maximum　11.23　mu　A　at　575　degrees　C　and　the　value　on　NO2　is　much　higher　than　other　gases　(CH4,　C2H4,　C3H6,　C3H8,　CO),　indicating　good　selectivity　for　detecting　NO2.　The　response　signals　of　the　sensor　were　slightly　affected　by　coexistent　O-2　varying　from　2　to　21　vol%　at　575　degrees　C.　The　response　current　value　decreased　only　4.9%　over　2　months,　exhibiting　the　potential　application　in　motor　vehicles.