Ammonia　is　a　carbon-free　energy　vector　and　has　attracted　great　attention　toward　＇zero-carbon　emission＇　and　＇energy　N-cycle＇　in　the　futuristic　energy　system.　In　this　work,　we　applied　perovskite　SrTiO3　oxides　as　anode　catalysts　in　NH3-fed　solid　oxide　fuel　cells　(NH3-SOFCs)　and　investigated　the　effects　of　cation-deficient　A　sites　and　Ni-doped　B　sites　on　the　conductivity　and　band　structure　by　a　series　of　characterizations.　The　results　showed　that　appropriate　A-site-deficient　Sr0.9Ti1-yNiyO3-δ　oxides　as　anodes　improve　the　electrochemical　performance　in　the　NH3-SOFCs,　while　a　negative　effect　was　found　for　the　B-site-deficient　cases.　Instead,　the　low　valence　Ni2+　arranged　at　B　sites　of　Sr0.9TiO3-δ　promote　the　reduction　of　Ti4+　to　Ti3+,　generating　oxygen　vacancies　and　then　facilitating　the　electron　migration　in　the　reaction.　Benefited　from　the　ex-solution　of　Ni　nanoparticles　(NPs),　the　optimal　powder　density　of　the　NH3-SOFC　by　electrolyte-supported　YSZ　is　obtained　over　the　Sr0.9Ti0.8Ni0.2O3-δ　(STN0.2),　reaching　287.1　and　262.7　mW·cm−2　in　H2　and　NH3　at　800　°C,　respectively,　presenting　a　high　utilization　rate　of　NH3.　The　activity　of　STN0.2　is　1.5-fold　higher　than　that　of　NH3-SOFC　adopting　NiO/YSZ　anode　under　the　same　conditions.　The　excellent　electrochemical　performance　of　STN0.2　is　attributed　to　small　flat-band　potential,　conduction　band,　band　gap　and　high　conductivity,　resulting　in　a　feasible　bound　electron　transition　to　free　electron.　Combining　distribution　of　relaxation　time　and　the　Bode　plots　analysis,　we　propose　the　preferential　reaction　mechanism　and　rate　determining　step.　©　2023