In　order　to　explore　the　optimal　conditions　of　nitrifying　sludge　granulation,　test　was　carried　out　in　a　sequencing　batch　reactor(SBR)　at　operation　conditions:　temperature　28°C,　aeration　0.2　m3　·　h-1,　dissolved　oxygen(DO)　＞　2.0　mg　·　L-1,　sludge　age(SRT)　15　d,　leading　to　settling　time　shorten　to　2　min.　The　granulation　of　nitrifying　floccular　activated　sludge　was　achieved　successfully　after　80　stable　cycles(19　d)　by　parameter　control　of　ammonia　oxidation　process,　by　optimization　of　aerobic　time　and　against　over-aeration,　and　average　diameter　of　sludge　granular　obtained　was　between　1.5-2.0　mm.　The　efficiency　of　COD　and　ammonia　removal　was　80%　and　95%,　respectively.　The　nitrite　accumulation　rate(NO2--N/NOx--N)　was　over　95%.　The　quantitative　results　from　fluorescence　in　situ　hybridization(FISH)　analysis　for　molecular　biology　show　that　the　dominant　micro-organism　was　still　AOB,　about　17.8%　of　total　bacteria,　while　NOB　only　0.6%.　The　main　factors　for　stable　performance　of　nitrification　were　FA　inhibition　and　real-time　control.　©　All　Rights　Reserved.