Landfill　leachate　was　treated　using　the　upflow　anaerobic　sludge　blanket　(UASB)　combined　with　anoxic/aerobic　reactor　(A/O)　for　shortcut　biological　nitrogen　removal.　The　treatment　performance　and　nitrous　oxide　(N2O)　emission　were　studied　under　different　salinity.　When　salinity　increased　from　10　to　35　g/L,　the　removal　efficiency　of　ammonium　nitrogen　and　total　nitrogen　decreased　from　99.3　to　83.9%　and　from　85.4　to　68.4%,　respectively　while　the　nitrite　accumulation　rate　always　remained　high　at　more　than　94.3%.　The　N2O　conversion　ratio　increased　by　14.7　times,　from　0.3　to　4.7%.　The　concentration　of　biodegradable　COD　in　influent　of　the　A/O　reactor　increased　with　the　increase　of　salinity,　which　lead　to　the　decrease　of　dissolved　oxygen　and　thus　stimulated　N2O　emission　remarkably　during　the　aerobic　zone.　Meanwhile,　the　N2O　emissions　were　likely　to　occur　by　a　combination　of　pathways　since　the　simultaneous　nitritation　and　denitritation　was　occurred　in　aerobic　zone.　The　increase　of　NH4+-N　concentration,　NO2--N　concentration　and　pH　caused　by　high　salinity　also　promoted　the　N2O　emission.　The　population　of　Nitrosomonas　europaea　increased　with　salinity,　which　was　important　for　N2O　emission.　(C)　2015　The　Korean　Society　of　Industrial　and　Engineering　Chemistry.　Published　by　Elsevier　B.V.　All　rights　reserved.