Bioaugmentation is an effective method of treating municipal wastewater with high ammonia concentration in sequencing batch reactors (SBRs) at low temperature (10°C). The cold-adapted ammonia- and nitrite- oxidizing bacteria were enriched and inoculated, respectively, in the bioaugmentation systems. In synthetic wastewater treatment systems, the average NH4+-N removal efficiency in the bioaugmented system (85%) was much higher than that in the unbioaugmented system. The effluent NH4+-N concentration of the bioaugmented system was stably below 8 mg·L^-1 after 20 d operation. In municipal wastewater systems with bioaugmentation, the effluent NH4+-N concentration was below 8 mg·L^-1 after 15 d operation. The average NH4+-N removal efficiency in unbioaugmentation system (about 82%) was lower compared with that in the bioaugmentation system. By inoculating the cold-adapted nitrite-oxidizing bacteria (NOB) into the SBRs after 10 d operation, the nitrite concentration decreased rapidly, reducing the NO2--N accumulation effectively at low temperature. The functional microorganisms were identified by PCR-DGGE, including uncultured Dechloromonas sp., uncultured Nitrospira sp., Clostridium sp. and uncultured Thauera sp. The results suggested that the cold-adapted microbial agent of ammonia-oxidizing bacteria (AOB) and NOB could accelerate the start-up and promote achieving the stable operation of the low-temperature SBRs for nitrification.