The　study　on　the　impact　factors　of　simultaneous　nitrification　and　denitrification　(SND)　in　the　Carrousel　oxidation　ditch　was　carried　out　based　on　pilot-scale　to　treat　low　C/N　urban　sewage.　With　the　effect　of　SND　in　the　oxidation　ditch,　the　system　could　achieve　the　best　removal　for　nitrogen　of　urban　sewage　with　low　C/N.　And　with　SRT　of　20　d,　R　of　50%,　MLSS　of　4000　mg/L,　the　ammonia,　total　nitrogen　(TN)　of　effluent　were　lower　than　5　mg/L,　13　mg/L,　respectively.　Based　on　this　the　kinetics　model　of　TN　removal　was　established,　which　could　control　the　concentration　of　TN　in　the　effluent　effectively　by　adjusting　HRT,　MLSS　and　other　parameters　in　the　oxidation　ditch,　which　would　provide　effective　theory　basis　for　optimization　and　adjustment　of　the　process.　©　2012　IEEE.