The　production　of　N2O　during　nitrogen　removal　from　real　domestic　wastewater　was　investigated　in　a　lab-scale　aerobic-anoxic　sequencing　batch　reactor　with　a　working　volume　of　14　L.　The　results　showed　that　the　total　N2O-N　production　reached　higher　than　1.87　mg/L,　and　up　to　4%　of　removed　nitrogen　was　converted　into　N2O.　In　addition,　N2O　led　to　a　much　higher　greenhouse　effect　than　CO2　during　aerobic　reaction　phase,　this　proved　that　N2O　production　could　not　be　neglected.　The　N2O-N　production　during　nitrification　was　1.85　mg/L,　whereas,　during　denitrification,　no　N2O　was　produced,　nitrification　was　the　main　source　of　N2O　production　during　nitrogen　removal.　Furthermore,　during　denitrification,　the　dissolved　N2O　at　the　end　of　aeration　was　found　to　be　further　reduced　to　N-2.　Denitrification　thus　had　the　potential　of　controlling　N2O　production.