This　study　focused　on　investigating　the　nitrogen　(N)　and　phosphorus　removal　characteristics　of　a　combined　enhanced　phosphorus　removal　(EBPR)　with　simultaneous　nitrification　and　denitrification　(SND)　process.　An　anaerobic/aerobic　operated　sequencing　batch　reactor　(SBR),　fed　with　actual　domestic　sewage　at　a　low　carbon/nitrogen　ratio　(C/N,　around　3.5),　was　studied　firstly　for　the　start-up　of　EBPR　and　the　enrichment　of　phosphorus　accumulating　organisms　(PAOs)　by　adjusting　the　influent　C/N,　and　lately　for　the　nutrient　removal　performance,　SND　efficiency,　and　carbon　sources　conversion　by　adjusting　the　dissolved　oxygen　(DO)　concentrations　at　the　aerobic　stage.　Results　showed　that　at　DO　concentration　of　around　2.0mg/L　and　influent　C/N　increased　from　3.2　to　7.5and　then　recovered　to　3.8,　effluent　PO43--P　concentration　gradually　decreased　from　3.9mg/L　to　below　0.5mg/L　accompanied　by　the　increase　of　anaerobic　phosphorus　release　amount　(PRA)　from　3.3mg/L　to　approximately　30mg/L.　Hereafter,　when　DO　concentration　gradually　decreased　to　about　1.0mg/L,　SND　became　obvious,　and　its　coupling　with　EBPR　increased　the　total　nitrogen　(TN)　and　PO43--P　removal　efficiencies　to　85%　and　94%,　respectively.　But　when　the　DO　concentration　was　continued　decreased　to　about　0.5mg/L,　nitrification　became　incomplete　and　nitrite　accumulation　became　obvious,　indicating　the　existence　of　simultaneous　partial　nitrification　and　denitrification.　The　results　indicated　that　the　combined　system　has　the　highest　nitrogen　and　phosphorus　removal　performance　at　DO　concentration　of　about　1.0mg/L.　In　addition,　when　DO　concentration　decreased　from　2.0mg/L　to　0.5mg/L,　the　contribution　of　PAOs　to　the　storage　of　anaerobic　intracellular　carbon　sources　(PPAO,　An)　gradually　reduced　from　30.3%　to　20.2%,　resulted　in　a　decrease　of　PRA　for　about　7mg/L.　DO　concentration　of　1.0~1.5mg/L　was　the　most　conducive　to　the　synthesis　of　carbon　source　PHA　in　the　anaerobic　stage　of　the　combined　system.　©　2018,　Editorial　Board　of　China　Environmental　Science.　All　right　reserved.