Partial　nitrification　is　crucial　for　application　of　autotrophic　nitrogen　removal　which　is　beneficial　for　treating　carbon-limited　wastewater.　This　study　presents　an　alternative　strategy　for　achieving　partial　nitrification　of　domestic　wastewater　treatment,　by　treating　activated　sludge　of　a　nitrifying　reactor　on　long-term　nitrite　exposure.　Initially,　the　nitrifying　reactor　obtained　complete　nitrification.　After　the　sludge　of　the　reactor　was　treated　with　nitrite　at　concentration　of　5-30　mg.L-1　without　feeding　for　32　days,　the　nitrite　accumulation　ratio　(NAR)　above　90%　was　achieved　in　30　days,　and　then　the　NAR　stabled　at　97.9%　under　low　temperature　of　16.6　degrees　C.　Further　analysis　showed　that　the　activity　decay　rate　of　ammonium-oxidizing　bacteria　(AOB)　(0.020　d(-1))　was　lower　than　that　of　nitrite-oxidizing　bacteria　(NOB)　(0.035　d(-1))　under　nitrite　stress.　Meanwhile,　the　NOB　were　effectively　suppressed　while　AOB　were　dominant.　These　observations　supported　the　feasibility　of　achieving　stable　partial　nitrification　by　treating　sludge　on　long-term　exposure　to　nitrite.