This study investigated the nitritation of domestic wastewater through the short-term addition of hydroxylamine (NH2OH). Sequencing batch reactor (SBR) was used and the NH2OH solution with an initial concentration of 5.0 mg/L was injected at each cycle. With NH2OH addition, the nitritation was quickly established in 5 d with nitrite accumulation ratio above 95%. Further, stable nitritation could be maintained without NH2OH addition in the following 53 days, even under unfavorable conditions (DO= 3 mg/L). According to qPCR results, NH2OH significantly reduced and continuously suppressed nitrite oxidizing bacteria (NOB), while the abundance of ammonia oxidizing bacteria was stable, induced the start-up and maintenance of nitritation. Among NOB, NH2OH significantly suppressed Nitrospira, while did not affect Nitrobactor. Nitrobactor gradually increased during the operation, which could induce the final deterioration of nitritation. Overall, this research provided the fundamental knowledge required to optimize the NH2OH addition strategy for operating a stable nitritation in domestic wastewater.