Domestic wastewater was treated by using three parallel sequencing batch reactors (SBR) at the pH of 7.9-8.0 to optimize aeration duration of partial nitrification. The partial nitrification was achieved and maintained by controlling the aeration time of t/2, t/4, t/8 respectively (t was aeration time) before appearance of "ammonia valley". Nitrite accumulation ratios were improved by 50％, 65％, 90％ respectively in the three reactors which were operated in 145 days. FISH quantitative analysis showed that the percentage of ammonia oxidizing bacteria (AOB) in the reactors increased differently. AOB and nitrite oxidizing bacteria (NOB) was 3.89％ and 0.27％ of the total bacteria respectively in No.3 reactor, which showed that AOB is the dominant bacteria in nitrifying bacteria. It is concluded that synergistic effect between the optimal control of aeration duration and the inhibition of FA would be the key factors to rapid start-up and maintain the stable nitrification.