Nitrous　oxide　(N2O)　is　one　of　the　three　main　greenhouse　gases　(CO2,　CH4,　N2O),　about　265　times　more　effective　than　carbon　dioxide　(CO2),　and　it　may　also　destruct　the　ozone　layer.　In　wastewater　biological　nitrogen　removal　process,　autotrophic　nitrification　has　been　thought　to　be　the　major　source　of　N2O　production.　In　this　study,　by　testing　the　production　of　N2O　under　different　conditions,　the　relationship　between　N2O　production　rate　and　ammonia　oxidation　rate　during　nitritation　process　was　investigated　in　a　laboratory　batch-scale　system　with　activated　sludge　for　treating　domestic　wastewater.　The　experimental　data　indicated　that　the　ammonia　oxidation　rate　(AOR)　increased　with　higher　DO　while　N2O　production　rate　(N2OR)　increased　first　then　decreased.　Besides　the　AOR　and　N2OR　were　by　varying　the　initial　ammonium　(NH4+-N)　concentration　in　batch　experiments.　The　max　N2OR　was　1.29　mg　N2O(g　MLVSS)-1·h-1　when　DO　was　0.6　mgL-1.　At　low　DO　level,　the　increase　of　AOR　would　promote　the　N2OR.　On　the　other　hand,　higher　AOR　might　not　produce　more　N2O　when　DO　was　high.　There　were　different　pathways　of　N2O　production　under　various　conditions　which　led　to　the　change　of　N2OR.　When　DO　was　low,　N2O　was　mainly　produced　by　nitrosyl　radical　(NOH),　while　increasing　AOR　promoted　the　N2OR　formation.　However,　nitrifier　denitrification　by　AOB　was　the　main　way　of　producing　N2O　at　high　DO　level.　This　pathway　might　be　inhibited　by　high　DO,　and　thus　even　there　was　high　AOR,　the　net　production　of　N2O　was　still　less.　In　addition,　the　existence　of　NH4+　was　very　important　to　N2O　production　too.　©　All　Right　Reserved.