The　effect　of　AOB/NOB　in　nitrifying　sludge　on　nitrification　characteristics　was　deeply　investigated　in　this　study.　Firstly,　activated　sludge　only　with　AOB　and　NOB　was　successfully　cultivated　in　two　same　SBRs　through　80　cycles,　respectively.　The　main　substrate　in　their　inflow　was　single,　during　cultivation　influencing　factors　were　controlled　and　sludge　was　discharged　at　regular　intervals.　Secondly,　the　ratio　of　abundance　between　AOB　sludge　and　NOB　sludge　was　determined　through　experiment　which　was　about　1:1.　Finally,　experiment　results　about　nitrification　characteristics　showed　that　nitrosation　rate,　ammonia　oxidation　rate,　nitrite　oxidation　rate　and　oxygen　uptake　rate　were　influenced　by　A/N　in　nitrifying　sludge.　A/N　should　be　close　to　1:0　for　steady　operation　of　partial　nitrification;　there　was　no　obvious　positive　relationship　between　ammonia　oxidation　rate　and　proportion　of　AOB　in　nitrifying　bacteria;　A/N　in　conventional　nitrification　sludge　for　municipal　sewage　treatment　should　not　less　than　1:2;　combined　with　online　monitoring　for　oxygen　uptake　rate,　when　it　became　stable,　the　startup　of　partial　nitrification　could　be　considered　as　nearly　achieved.　©　2016,　Editorial　Board　of　China　Environmental　Science.　All　right　reserved.