Cu-SSZ-13　and　CuO/SSZ-13　catalysts　were　prepared　by　ion　exchange　and　impregnation　methods,　respectively　and　tested　for　selective　catalytic　oxidation　of　NH3　(NH3-SCO).　Cu-SSZ-13(2)　catalyst,　which　was　prepared　by　ion　exchange　for　two　times,　performed　the　best　in　improving　NH3　conversion　and　N2　selectivity　at　low　temperatures　(≤200).　Effects　of　O2　content　and　gas　hourly　space　velocity　(GHSV)　on　the　oxidation　of　NH3　over　Cu-SSZ-13(2)　were　investigated.　Physicochemical　characteristics　of　the　catalysts　and　the　surface　reaction　process　were　characterized　by　N2　adsorption-desorption,　XRD,　NH3-TPD　and　NH3-TPSR　techniques.　The　results　showed　that　NH3　conversion　and　N2　selectivity　reached　98.5%　and　92.2%,　respectively　at　200　over　Cu-SSZ-13(2).　With　the　increase　of　O2　content,　NH3　conversion　at　low　temperatures　increased,　but　N2　selectivity　decreased.　With　the　increase　of　GHSV,　NH3　conversion　at　low　temperatures　decreased,　but　N2　selectivity　was　hardly　affected.　Low　N2　selectivity　for　NH3　oxidation　at　low　temperatures　(≤200)　over　Cu-SSZ-13　and　CuO/SSZ-13　was　mainly　due　to　the　formation　of　N2O　by-product.　Compared　with　CuO/SSZ-13,　Cu-SSZ-13(2)　had　larger　values　of　specific　surface　area,　pore　volume　and　pore　size,　less　CuO　and　more　Lewis　and　Brønsted　acid　sites　on　the　surface,　which　might　explain　the　higher　NH3　conversion　and　N2　selectivity　obtained　at　low　temperatures　over　Cu-SSZ-13(2).　Apart　from　N2O,　NO　and　NO2　by-products　were　also　detected　during　the　NH3-TPSR　process　over　Cu-SSZ-13(2).　It　could　be　inferred　that　NH3-SCO　over　Cu-SSZ-13(2)　followed　the　internal　selective　catalytic　reduction　(iSCR)　mechanism　considering　the　fact　that　NO　and　NO2　selectivity　increased　with　the　increase　of　GHSV　at　low　temperatures.　©　2023　Chinese　Society　for　Environmental　Sciences.　All　rights　reserved.