The　N2O　production　in　two　nitrogen　removal　processes　treating　domestic　wastewater　was　investigated　in　laboratory-scale　aerobic-anoxic　sequencing　batch　reactors　(SBRs).　Results　showed　that　N2O　emission　happened　in　the　aerobic　phase　rather　than　in　the　anoxic　phase.　During　the　aerobic　phase,　the　nitrogen　conversion　to　N2O　gas　was　27.7%and　36.8%　of　NH　(4)　(+)　-N　loss　for　conventional　biologic　N-removal　process　and　short-cut　biologic　N-removal　process.　The　dissolved　N2O　was　reduced　to　N-2　in　the　anoxic　denitrification　phase.　The　N2O　production　rate　increased　with　the　increasing　of　nitrite　concentration　and　ceased　when　NH　(4)　(+)　-N　oxidation　was　terminated.　Higher　nitrite　accumulation　resulted　in　higher　N2O　emission　in　the　short-cut　nitrogen　removal　process.　Pulse-wise　addition　of　20　mg　NO　(2)　(-)　-N　center　dot　L-1　gave　rise　to　3-fold　of　N2O　emission　in　the　conventional　N-removal　process,　while　little　change　happened　with　20　mg　NO　(3)　(-)　-N　center　dot　L-1　was　added　to　SBR1.