Nitrous oxide (N₂O) is a powerful greenhouse gas, and also the main compound causing stratospheric ozone depletion. The ocean is an important source of N₂O emission to the atmosphere, and N₂O in the ocean is mainly produced by the microbial-mediated nitrogen biogeochemical cycle. This paper firstly reviews the marine N₂O emission flux, the distribution characteristics of seawater N₂O and environmental impact factors. Then, the microbial processes regulating the N₂O production and emission are discussed. At last, we address the N₂O biogeochemical process based on the relationship between low oxygen and N₂O production in the estuarine and coastal ecosystems.