The　catalytic　combustion　of　NH3　to　produce　nitrogen　(N2)　and　water　(H2O)　is　a　promising　method　to　solve　high　ignition　temperature　with　more　NOx　production　and　poor　combustion　stability　in　the　carbon-free　fuel　utilization　of　NH3.　This　study　focuses　on　distinct　structure-activity　relationship　over　CuO/CeO2　series　catalysts　and　reaction　mechanism　for　catalytic　NH3　combustion.　Cu/Ce-Sphere,　Cu/Ce-Rod,　and　Cu/Ce-Octahedron　catalysts　were　synthesized　through　an　impregnation　method　by　using　different　CeO2　carriers　(nano　sphere　(S),　rod　(R)　and　octahedron　(O)).　The　activity　for　NH3　combustion　followed　an　order　of　Cu/Ce-S　＞　Cu/Ce-R　＞　Cu/Ce-O　＞　Ce-S.　The　better　activity　of　Cu/Ce-S　is　attributed　to　the　strong　interaction　between　CuO　and　Ce-S　(111　and　220　planes)　at　the　interface　of　oxide　phases.　This　interaction　is　indicative　of　a　higher　specific　surface　area　(SSA)　to　promote　CuOx　dispersion,　facilitating　the　adsorption　of　ammonia.　Additionally,　more　Cu-Ox-Ce　solid　solution　with　oxygen　vacancies　enhances　the　formation　and　mobility　of　active　oxygen　species.　The　Cu/Ce-S　showed　a　low　NH3　lean-combustion　limits　of　7.6　%　NH3　to　keep　self-sustained　combustion,　and　realized　a　high　NH3　conversion　(∼100　%)　and　effective　N2　yield　(∼98.0　%)　with　low　NOx　formation　over　360　min.　The　reaction　pathways　for　NH3　combustion　over　Cu/Ce-S　were　revealed　by　the　NH3–TPD/TPR-mass　spectrometer,　isotopic　(18O2)　transient　exchange　experiment　and　in　situ　infrared　transmission　spectroscopy　(IR).　The　Mars-van-Krevelen　(M–K)　mechanism　plays　a　crucial　contribution　of　adsorbed　NHx　by　ammonia　dehydrogenation　route　to　react　with　active　lattice　oxygen,　and　to　produce　N2　and　H2O.　Additionally,　the　subordinate　contribution　of　Langmuir–Hinshelwood　(L–H)　mechanism　refers　the　reaction　of　adsorbed　NHx　species　and　chemisorbed　oxygen　or　adsorbed　HNO　through　oxidation　route.　These　results　demonstrate　the　viability　of　environmentally　friendly　catalytic　combustors　for　ammonia　fuel　in　the　future,　and　also　advance　the　understanding　of　reaction　mechanism　for　catalytic　ammonia　combustion.　©　2024