Through　real-time　aeration　duration　control,　partial　nitrification　was　carried　out　in　a　lab-scale　SBR　at　normal　temperatures　and　maintained　for　a　long　time　even　at　low　temperatures.　The　specific　ammonia　oxidation　rate　would　be　reduced　with　decrease　of　the　temperature.　The　average　specific　ammonia　oxidation　rate　at　27°C　was　1.68　times　of　that　at　13°C.　The　temperature　coefficient　of　ammonia　oxidation　reaction　in　the　reactor　was　ascertained　1.501　according　to　the　Arrhenius　expression.　When　nitrite　accumulation　ratio　was　steadily　kept　over　90%,　fluorescence　in　situ　hybridization　(FISH)　was　used　to　detect　the　sludge　population　structure,　which　showed　the　proportion　of　the　ammonia-oxidizing　bacteria　(AOB)　and　nitrite-oxidizing　bacteria　(NOB)　was　8%~9%　and　lower　than　0.5%,　respectively.　The　real-time　control　strategy　had　a　positive　effect　on　the　enrichment　of　AOB　and　the　limitation　or　wash-out　of　NOB.　An　advisable　start　up　strategy　to　operate　a　partial　nitrification　system　at　low　temperatures　could　have　two　steps,　obtaining　firstly　the　selective　enrichment　of　AOB　as　well　as　the　washout　of　NOB　by　real-time　aeration　duration　control　under　ordinary　temperatures,　and　then　making　the　biomass　slowly　adapt　to　low　temperatures.