Nutrient biogeochemical cycling in the tidal flat ecosystem is not only one of the key studying contents of IGBP and LOICZ projects, but also the important component in the study of global change and region Response. Coast and tidal flat is an open and complex ecosystem. A lot of nitrogen nutrient may be directly transported into coastal zone through riverine input, penetration of groundwater, atmospheric deposition and the exchange with offshore water. Some findings showed that atmospheric inputs made the main contribution to the source of nitrogen in the coastal and tidal flat ecosystem. In addition, the decomposition of organic matter accumulated in the tidal sediment is also an important source of nitrogen. In recent years, some researchers have tried to source nitrogen by using carbon and nitrogen isotopes in organic matter in the tidal flat ecosystem. Nitrogen cycling has the important and ecological significance to primary products in the tidal flat ecosystem. Therefore, the processes of nitrogen cycling in the tidal flat ecosystem, e.g. nitrogen fixation, nitrification and denitrifciation, have well been studied in the last decades. Many references reported the effects of environmental factors and sediment physiochemical parameters on the processes of nitrogen cycling including physical, chemical and biological process of nitrogen transportation and transformation. Benthic benthos is an important component of the tidal flat ecosystem， which plays a key role in the nitrogen cycling in the tidal flat ecosystem. It has been reported that benthic benthos had the important effects on the processes of nitrogen cycling in tidal flat. In addition, the trend of the study on nitrogen biogeochemistry cycling in the tidal flat ecosystem was also expatiated in the paper.