Effects　of　concentrations　of　PO43-,　Mg2+　and　NH4+　on　their　recovery　rates　from　synthetic　sludge　dewatering　filtrate　and　struvite　crystal　purity　are　studied　in　a　batch　sequencing　reactor.　Results　show　that　the　recovery　rate　of　PO43-　increases　with　higher　initial　concentrations　of　PO43-,　Mg2+　and　NH4+　in　equal　moles.　The　recovery　rate　of　PO43-　has　a　line　relationship　with　the　natural　logarithm　of　an　initial　mole　concentration　of　PO43-,　Mg2+　or　NH4+.　The　recovery　rate　of　Mg2+　is　higher　or　equal　to　the　recovery　rate　of　PO43-.　The　initial　concentration　of　Mg2+　is　a　key　limiting　factor　for　PO43-　recovery.　The　recovery　rate　of　NH4+　is　less　than　that　of　Mg2+　and　PO43-　by　20%　in　all　batch　tests.　The　initial　concentration　of　NH4+　has　a　big　effect　on　the　purity　of　struvite.　When　the　concentration　of　NH4+/PO43-　in　mole　increases　to　2.0,　the　purity　of　the　struvite　crystallization　increases　to　95%.