For　enhancing　the　partial　nitritation-anammox　(PN/A)　process,　the　effects　of　granule　fraction　on　system　performance　were　investigated　in　this　study.　Two　sequencing　batch　reactors　(SBRs)　were　inoculated　with　PN/A　biomass　with　a　floc　mass　fraction　of　53%.　In　SBR1,　when　the　nitrogen　removal　rate　(NRR)　was　stable,　flocculent　sludge　was　gradually　discharged　from　the　reactor　using　a　screen,　and　the　granule　fraction　was　therefore　increased.　However,　nitrogen　removal　was　not　improved　and　finally　deteriorated　due　to　the　loss　of　nitritation　activity.　In　SBR2,　most　flocculent　sludge　was　eliminated　and　granular　proportion　was　maintained　at　over　90%　by　controlling　a　short　settling　and　decanting　time.　NRR　was　low　initially　but　gradually　improved　to　1.23　kg　N/(m(3).d),　which　was　54%　higher　than　SBR1.　Ammonium　oxidation　activities　of　flocs　and　granules　were　respectively　measured.　Results　suggested　that　the　increase　of　nitritation　activity　in　the　granules　was　the　main　reason　for　the　improvement　of　nitrogen　removal　in　SBR2.