Nitrogen is an essential nutrient for the growth of all living organisms in the ocean. Its cycling processes and its close coupling with the cycle of biological elements such as carbon and phosphorus jointly regulate the structure and function of marine ecosystem. Nitrite serves as a key intermediate in oceanic nitrogen cycle， and plays an important role in various nitrogen transformation processes such as nitrification， denitrification， anammox， nitrate bioabsorption. Nitrogen and oxygen isotopes of nitrite are newly developed technologies， which have unique value in identifying the source and sink processes of oceanic nitrite， explaining the transport and transformation of various nitrogen components， as well as revealing the nitrogen cycling in the oxygen-deficient zones. In recent years， nitrogen and oxygen isotopes of nitrite have been widely applied in the oceanic regions such as the Arabian Sea， the eastern tropical North Pacific， the eastern tropical South Pacific， the South China Sea and the East China Sea. These studies revealed the reasons for the accumulation of nitrite in oceanic euphotic zone and oxygen-deficient zones， the production mechanism of nitrous oxide in the ocean， the biogeochemical cycle of nitrogen in the oxygen-deficient zones， as well as the isotope exchange dynamics of nitrogen in an isotopic exchange reaction between nitrate and nitrite， which greatly deepened our understanding of nitrogen cycle in marine environment. In terms of the future development trend of ocean nitrogen cycle research， it is still necessary to strengthen research in several fields， such as the biogeochemical processes of nitrite in the euphotic zone and the oxygen-deficient zones， the dynamics of the nitrogen and oxygen isotope exchange systems in the isotope exchange reaction between nitrate and nitrite. In this way， the path of the ocean nitrogen cycle can be described more accurately， and the nitrogen budget in marine environment can be established quantitatively.