This　study　investigated　the　nitritation　of　domestic　wastewater　through　the　short-term　addition　of　hydroxylamine　(NH2OH).　Sequencing　batch　reactor　(SBR)　was　used　and　the　NH2OH　solution　with　an　initial　concentration　of　5.0　mg/L　was　injected　at　each　cycle.　With　NH2OH　addition,　the　nitritation　was　quickly　established　in　5　d　with　nitrite　accumulation　ratio　above　95%.　Further,　stable　nitritation　could　be　maintained　without　NH2OH　addition　in　the　following　53　days,　even　under　unfavorable　conditions　(DO=　3　mg/L).　According　to　qPCR　results,　NH2OH　significantly　reduced　and　continuously　suppressed　nitrite　oxidizing　bacteria　(NOB),　while　the　abundance　of　ammonia　oxidizing　bacteria　was　stable,　induced　the　start-up　and　maintenance　of　nitritation.　Among　NOB,　NH2OH　significantly　suppressed　Nitrospira,　while　did　not　affect　Nitrobactor.　Nitrobactor　gradually　increased　during　the　operation,　which　could　induce　the　final　deterioration　of　nitritation.　Overall,　this　research　provided　the　fundamental　knowledge　required　to　optimize　the　NH2OH　addition　strategy　for　operating　a　stable　nitritation　in　domestic　wastewater.