In　this　study,　a　sequencing　batch　reactor　(SBR)　was　used　to　treat　domestic　wastewater,　and　the　optimal　aeration　rate　and　time　to　realize　partial　nitritation　(PN,　NH4+-N　was　partially　converted　to　NO2--N)　were　obtained　through　three　preliminary　tests.　A　long-term　PNSBR　was　operated　more　than　110　d　(450　cycles)　with　an　optimal　aeration　rate　[7.2-12　L(hL)-1]　and　time　(2-3　h)　during　aeration.　The　results　showed　that　the　nitrite　accumulation　rate　in　the　effluent　maintained　94%-100%,　indicating　the　stable　partial　nitrification.　The　ratios　between　NO2--N　and　NH4+-N　were　in　the　range　of　2-4.　Further　analysis　demonstrated　that　in　the　long-term　operation　of　PNSBR,　the　low　dissolved　oxygen　(DO)　by　controlling　aeration　benefited　the　ammonia　oxidizing　bacteria　(AOB)　activity　but　inhibited　the　nitrite　oxidizing　bacteria　(NOB)　one.　On　the　other　hand,　the　residual　nitrite　after　decanting　in　a　cycle　was　removed　via　denitrification　(endogenous　in　this　cycle　and　exogenous　in　next　cycle)　by　using　organics　in　raw　wastewater,　through　which　substrates　for　NOB　were　prohibited,　and　thus　stable　PN　was　realized.　The　process　of　simultaneous　anammox　and　denitrification　(SAD)　was　widespread,　and　PNSBR,　as　a　pre-treatment　reactor,　can　provide　substrates　for　SAD,　and　thus　PN　was　a　potential　technology　in　future.　©　All　Right　Reserved.