At　room　temperature　conditions　[(22±1)],　by　using　SBR　reactor,　it　is　explored　that　how　delay　aeration　impact　nitrosation　stability　for　low　ammonia　nitrogen　sewage　and　efficient　recovery　strategy　for　nitrosation　instability　because　of　delay　aeration　is　looked　for.　Results　show　that　the　delay　aeration　creates　a　favorable　environment　to　NOBs　so　that　NOBs　can　reproduce　rapidly,　delay　aeration　of　1h　for　the　23d　eventually　makes　the　nitrosation　system　instability;　nitrosation　instability　needs　to　adopt　a　joint　recovery　strategy　that　the　additional　1　h　front　stir　anaerobic　phase　and　control　of　ammonia　oxidation　rate　at　about　50%　by　shortening　the　aeration　time　is　carried　out.　Then　nitrosation　can　be　realized　through　60cycle　(20d).