Abstract: A system for reducing emission of nitrous oxide during sewage treatment, including: a regulating pool, a first aerobic constructed wetland, an anoxic pool, and a second aerobic constructed wetland. The water outlet of the regulating pool is connected to the water inlet of the top of the first aerobic constructed wetland via a pipe and a first control valve. The first aerobic constructed wetland includes sequencing batch constructed wetlands arranged in parallel. A branch pipe and a second control valve are disposed on the pipe between the regulating pool and the first aerobic constructed wetland. The outlet of the branch pipe and the water outlet of the first aerobic constructed wetland are combined together and connected to the water inlet of the bottom part of the anoxic pool. The anoxic pool is an upward flow biological filter.