The　present　work　demonstrated　the　heterovalent　ions　incorporated　pyrochlore　Sm2Zr2O7　ceramic　with　high　NO2　sensitivity　through　molecular　insights　into　the　bond　of　[BO6]　unit　and　the　sensing　mechanism.　An　effective　B-site　strategy　was　developed　to　prepare　a　series　of　defective　Sm2Zr1.95X0.05O7　+　delta　(SZX,　X=　Mn2+,　Ga3+,　Sn4+,　Nb5+,　W6+)　ceramics　to　create　oxygen　vacancies　or　interstitial　oxygen　induced　which　enhances　the　NO2　sensing　performances.　The　structural　analyses　carried　out　by　XRD,　SEM,　XPS,　Raman　and　the　NO2　adsorption　on　a　cold　surface　of　the　sensor　clarified　the　potential　sensing　mechanism.　The　electrochemical　results　clearly　indicate　that　NO2　sensing　properties　are　closely　related　to　the　valence　of　doped　cations.　The　sensor　of　Sm2Zr2O7　with　Nb5+　arranged　at　B　sites　indicates　high　sensitivity,　quick　response/recovery　speed,　excellent　selectivity　and　stability　compared　with　others,　exhibiting　great　application　prospects　for　the　automotive　equipment.