In　this　study,　a　sequencing　batch　reactor　(SBR)　treatment　system　operating　in　anoxic　/aerobic　(A/O)　mode　was　established,　and　the　optimization　of　hydroxylamine　dosing　point　on　partial　nitrification　of　municipal　wastewater　was　explored.　Results　of　batch　experiments　showed　that　the　presence　of　dissolved　oxygen　could　reduce　the　inhibitory　effect　of　hydroxylamine　on　NOB　by　(20±0.5)%.　In　addition,　compared　with　the　treatment　without　anoxic　condition　and　extended　anoxic　duration　(＞15min),　the　activity　inhibited　ratio　of　NOB　increased　by　13%　~　25%　with　anoxic　duration　of　1~5min.　The　long-term　experiments　showed　that　the　NO2--N　accumulation　rate　of　the　partial　nitrification　system　with　hydroxylamine　addition　at　the　end　of　anoxic　stage　maintained　above　92%,　while　it　decreased　gradually　with　hydroxylamine　at　aerobic　stage.　QPCR　analysis　showed　that　the　inhibition　on　ammonia　oxidizing　bacteria　(AOB)　could　be　reduced　with　sufficient　inhibition　on　NOB　when　the　hydroxylamine　was　added　at　the　end　of　anoxic　period,　facilitating　the　dominance　of　AOB　in　microbial　community　structure.　This　study　provides　a　theoretical　basis　for　optimizing　hydroxylamine　dosing　point　and　maintaining　stable　partial　nitrification　process.　©　2021,　Editorial　Board　of　China　Environmental　Science.　All　right　reserved.