Simultaneous　biological　phosphorus　and　nitrogen　removal　by　enhanced　anoxic　phosphate　uptake　was　investigated　in　an　anaerobic-aerobic-anoxic-aerobic　sequencing　batch　reactor　(model　II).　The　ratio　of　the　anoxic　phosphate　uptake　to　the　aerobic　phosphate　uptake　capacity　increased　from　28.2%　to　68.3%　by　insert　an　anoxic　phase　in　an　anaerobic-aerobic　SBR　(model　I).　The　model　II　SBR　system　showed　stable　phosphorus　and　nitrogen　removal　performance.　Average　removal　efficiencies　of　ρ(COD),　ρ(PO3--P),　and　ρ(TN)　were　92.0%,　98.0%,　and　81.5%,　respectively.　Through　batch　experiment,　it　was　found　that　ρ(NO2--N)　(up　to　30　mg/L)　was　not　detrimental　to　the　anoxic　phosphate　uptake　and　could　serve　as　an　electron　acceptor　like　ρ(NO3--N).　In　fact,　the　phosphate　uptake　rate　was　even　faster　in　the　presence　of　ρ(NO2--N)　as　an　electron　acceptor　compared　to　the　presence　of　ρ(NO3--N).　It　was　found　that　on-line　sensor　values　of　pH　and　EORP　were　somehow　related　with　the　dynamic　behaviors　of　nutrient　concentrations　(ρ(COD),　ρ(NH4+-N),　ρ(NO3--N),　and　ρ(PO33--P))　in　the　SBR.　The　inflexion　of　EORP　profile　corresponding　to　the　end　of　phosphorus　released　in　anaerobic　phase;　the　inflexion　of　EORP　and　pH　profiles　corresponding　to　the　end　of　nitrification　in　aerobic　phase　I;　the　inflexion　of　EORP　and　pH　profiles　corresponding　to　the　end　of　denitrification　in　anoxic　phase;　the　inflexion　of　EORP　and　pH　profiles　corresponding　to　the　end　of　ρ(COD)　exhaust　and　phosphorus　uptake　in　aerobic　phase　II.　These　pH　and　EORP　profile　characteristic　point　could　be　used　as　real-time　control　parameters　to　adjust　the　duration　of　each　operational　phase　in　the　model　II　SBR,　thus　could　enhance　the　nitrogen　and　phosphorus　removal　efficiency.