Designing　a　cost-effective　and　fast　fabrication　Cu-SSZ-13　with　improved　selective　catalytic　reduction　of　NO　by　ammonia　(NH3-SCR)　performance　remains　an　open　question.　Here　we　report　that　LaCe-SSZ-13　zeolites　were　synthesized　from　spent　fluid　catalytic　cracking　catalyst　within　12　h.　After　ion-exchanging　with　CuSO4　solution,　the　obtained　LaCeCu-SSZ-13　catalysts　exhibit　significantly　higher　catalytic　activity　and　hydrothermal　stability　than　conventional　Cu-SSZ-13.　Various　characterizations　reveal　that　La　and　Ce　modification　not　only　facilitates　the　disperse　of　isolated　Cu2+　species,　but　also　effectively　mitigates　dealumination　and　inhibits　copper　species　aggregation　after　hydrothermal　aging.　In-situ　diffuse　reflection　infrared　Fourier　transform　spectrum　analyses　demonstrate　that　La　and　Ce　modification　can　accelerate　the　adsorption　capacity　for　NH3　and　NOx　and　promote　the　decomposition　of　NH4NO3　intermediate　species　on　the　catalyst,　benefiting　the　improvement　of　low　-temperature　activity.　The　combination　of　experiments　and　theoretical　calculations　further　demonstrate　that　the　most　stable　positions　of　La　and　Ce　are　on　different　eight-membered　rings　in　SSZ-13,　and　then　Cu2+　ions　tend　to　enter　eight-membered　rings　to　enhance　the　NH3　adsorption　capacity　and　decrease　the　H2O　adsorption　capacity,　which　results　in　higher　low-temperature　activity　and　hydrothermal　stability　than　Cu-SSZ-13.　Our　work　provides　a　feasible　strategy　for　preparing　the　efficient　rare-earth-modified　Cu-zeolite　based　NH3-SCR　catalyst　for　nitrogen　oxide　abatement.