The　ever-increasing　demand　for　nitrogen　oxides　(NOx)　emission　control　from　diesel　engines　during　cold　start　period　has　provided　a　strong　impetus　to　improve　the　low-temperature　NOx　removal　efficiency　of　Cu/SSZ-13　catalyst.　In　this　work,　a　series　of　bimetallic　catalysts　CuCo/SSZ-13　with　varying　cobalt　contents　were　prepared,　and　attained　the　significant　performance　enhancement　in　NH3　selective　catalytic　reduction　(NH3-SCR)　reaction.　The　promotion　mechanism　of　these　catalysts　at　low　temperatures　(＜　200　°C)　was　proposed:　(1)　The　introduced　Co(II)　ions　could　tune　the　distributions　of　copper　species　and　acid　sites,　resulting　in　a　higher　ratio　of　ZCuOH/Z2Cu　(Z　represents　a　negatively　charged　site　on　zeolite　framework)　and　much　more　Lewis　acid　sites　compared　with　original　Cu/SSZ-13.　(2)　The　fast　reaction　of　reactive　bridging　nitrates　with　NH3　adsorbed　on　Lewis　acid　sites　via　Langmuir-Hinshelwood　(L-H)　mechanism　decreased　the　activation　energy.　However,　the　addition　of　high　cobalt　content　facilitated　the　formation　of　inactive　CuOx　species,　which　was　not　conducive　to　maintaining　high-temperature　(＞　500　°C)　activity.　©　2023　Elsevier　B.V.