In　this　study,　it　was　investigated　the　nitrogen　removal　(NR)　performance　and　potential　mechanism　for　high　C/N　wastewater　treatment　under　different　dissolved　oxygen　(DO)　concentrations.　The　results　showed　that　DO　con-centration　significantly　affected　the　removal　efficiency　of　total　nitrogen　(TN).　When　the　initial　DO　increased　from　0.5　to　1.5　mg/L,　TN　removal　efficiency　significantly　increased　from　65　%　to　85　%.　However,　a　further　DO　in-crease　did　not　promote　TN　removal,　and　the　NR　was　only　80　%　with　an　initial　DO　concentration　of　3.5　mg/L.　The　effect　of　DO　concentration　on　NR　was　influenced　by　the　combined　action　of　functional　bacteria　and　electron　flow.　Excessive　DO　concentration　did　not　positively　affect　NR　efficiency　but　promoted　electron　utilization　and　res-piratory　proliferation.　When　the　DO　concentration　was　1.5　mg/L,　more　electrons　generated　by　sodium　acetate　metabolism　were　transferred　to　the　aerobic　denitrification　process,　compared　to　when　the　DO　concentration　was　3.5　mg/L.