Effects　of　the　constitutes　of　sludge　dewatering　filtrate　on　phosphorus　recovery　in　form　of　struvite　(MgNH4PO4·6H2O)　were　studied　by　using　batch　stirring　reactors.　The　results　showed　that　with　keeping　stirring　speed　at　200　rpm,　stirring　time　at　180　min　and　precipitation　time　at　60　min　in　all　experiments,　pH　of　sludge　dewatering　filtrate　rose　after　stirring　without　reagent　addition;　however,　it　was　not　enough　to　form　struvite.　When　the　concentration　of　PO43-　was　at　4.00　mmol/L,　more　than　90%　of　the　PO43-　was　recovered.　But　only　the　initial　concentration　of　Mg2+　in　sludge　dewatering　filtrate　exceeded　above　5.00　mmol/L,　the　reaction　between　Ca2+　and　PO43-　was　inhibited　distinctly　and　the　ratio　of　the　recovery　molar　concentration　of　PO43-,　Mg2+　and　NH4+　could　nearly　reach　1:1:1.　which　means　that　the　most　quantity　struvite　were　formed.　When　pH　ranged　from　10.0　to　10.5,　the　most　quantity　of　struvite　formed.　Turbidity　of　sludge　dewatering　filtrate　had　negative　effect　on　the　recovery　of　Mg2+　and　struvite　formation.