A　lab-scale　anaerobic/aerobic　sequencing　batch　reactor　(SBR)　was　operated　to　investigate　its　performance　in　biological　nutrient　removal　from　domestic　wastewater,　particularly　regarding　the　effect　of　nitrite　accumulation　resulting　from　short-cut　nitrification　on　biological　phosphorus　removal　(BPR).　Short-cut　nitrification　was　successfully　achieved　by　controlling　low　DO　concentration　(0.5~1.0　mg·L-1)　and　aerobic　duration.　The　results　showed　that　less　than　10　mg·L-1　of　nitrite　had　no　effect　on　phosphate　uptake　and　release　with　PO43--P　concentrations　in　the　aerobic　effluent　of　below　1　mg·L-1;　whereas　a　significant　decrease　of　phosphate　uptake　and　release　with　the　effluent　PO43--P　concentration　of　5　mg·L-1　was　observed　when　nitrite　accumulation　reached　20　mg·L-1,　indicating　deterioration　of　BPR.　After　adding　external　carbon　sources　(initial　COD　concentration　of　200　mg·L-1),　BPR　performance　recovered　after　20　days.　The　results　suggest　that　the　25~30　mg·L-1　of　nitrite　accumulated　during　the　aeration　period　did　not　inhibit　aerobic　phosphate　uptake.　The　main　reason　for　poor　phosphorus　removal　was　that　the　presence　of　nitrite　in　the　anaerobic　period　caused　denitrifying　bacteria　to　compete　with　phosphate　accumulating　organisms　(PAOs)　for　limited　carbon　sources.　Lowered　poly-β-hydroxyalkanoate　(PHA)　synthesis　in　PAOs　led　to　decreased　phosphate　uptake　in　the　aerobic　stage.　Batch　experiments　were　performed　to　investigate　the　effect　of　nitrite　on　PAOs　under　anaerobic　conditions,　which　indicated　that　nitrite　as　an　inhibitor　at　a　concentration　of　30　mg·L-1　would　not　inhibit　the　anaerobic　phosphate　release.　When　sufficient　carbon　source　was　provided,　nitrite　of　30　mg·L-1　had　no　impact　on　PHA　storage;　contrarily,　when　the　carbon　source　was　insufficient,　denitrifying　bacteria　competing　for　carbon　source　with　PAOs　resulted　in　a　decrease　of　PHA　synthesis　and　phosphate　release.