The　characteristics　of　anaerobic　phosphorus　release　and　anoxic　phosphorus　uptake　were　investigated　in　sequencing　batch　reactors　using　denitrifying　phosphorus　removing　bacteria　(DPB)　sludge.　The　lab-scale　experiments　were　accomplished　under　conditions　of　various　nitrite　concentrations　(5.5,　9.5,　and　15　mg/L)　and　mixed　liquor　suspended　solids　(MLSS)　(1844,　3231,　and　6730　mg/L).　The　results　obtained　confirmed　that　nitrite,　MLSS,　and　pH　were　key　factors,　which　had　a　significant　impact　on　anaerobic　phosphorus　release　and　anoxic　phosphorus　uptake　in　the　biological　phosphorous　removal　process.　The　nitrites　were　able　to　successfully　act　as　electron　acceptors　for　phosphorous　uptake　at　a　limited　concentration　between　5.5　and　9.5　mg/L.　The　denitrification　and　dephosphorous　were　inhibited　when　the　nitrite　concentration　reached　15　mg/L.　This　observation　indicated　that　the　nitrite　would　not　inhibit　phosphorus　uptake　before　it　exceeded　a　threshold　concentration.　It　was　assumed　that　an　increase　of　MLSS　concentration　from　1844　mg/L　to　6730　mg/L　led　to　the　increase　of　denitrification　and　anoxic　P-uptake　rate.　On　the　contrary,　the　average　P-uptake/N　denitrifying　reduced　from　2.10　to　1.57　mg　PO43--P/mg　NO3--N.　Therefore,　it　could　be　concluded　that　increasing　MLSS　of　the　DEPHANOX　system　might　shorten　the　reaction　time　of　phosphorus　release　and　anoxic　phosphorus　uptake.　However,　excessive　MLSS　might　reduce　the　specific　denitrifying　rate.　Meanwhile,　a　rapid　pH　increase　occurred　at　the　beginning　of　the　anoxic　conditions　as　a　result　of　denitrification　and　anoxic　phosphate　uptake.　Anaerobic　P　release　rate　increased　with　an　increase　in　pH.　Moreover,　when　pH　exceeded　a　relatively　high　value　of　8.0,　the　dissolved　P　concentration　decreased　in　the　liquid　phase,　because　of　chemical　precipitation.　This　observation　suggested　that　pH　should　be　strictly　controlled　below　8.0　to　avoid　chemical　precipitation　if　the　biological　denitrifying　phosphorus　removal　capability　is　to　be　studied　accurately.