This paper aimed to reveal the dynamic changes of the concentrations of nitrogen transformation intermediates and the emission of the greenhouse gas nitrous oxide (N 2 0) of the activated sludge with pulse aeration. The results indicated that the total nitrogen (TN) removal performed better and there were no nitrite and nitrate accumulation in the pulse aerated reactor. Specific oxygen utilization rate (SOUR) and dehydrogenase activity (DHA) of the activated sludge with pulse aeration were lower than those with continuous aeration, which was in agreement with the COD removal efficiency. The specific ammonia utilization rate (SAUR) and the specific nitrite utilization rate (SNUR) decreased with time from 0.43 to 0.32 mg/(g MLSS.min) and from 0.28 to 0.12 mg/(g MLSS.min), respectively. Meanwhile, the nitrate reductase activity (NARA) and the nitrite reductase activity (NIRA) enhanced from 0.93 to 1.67 mg/(mL.d) and from 1.19 to 1.62 mg/(mL.d), respectively. The advance of NIRA in the denitrification process played a more important role in the non-accumulation of nitrite, which led to less N2O emission by pulse aeration. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.