The predominance of nitrogen fixing cyanobacteria in the eutrophic aquatic systems is related to many environmental factors, such as nutrient forms and concentrations, nitrogen to phosphorus ratio, water temperature and trace metal. The nitrogen fixing cyanobacteria dominated in lakes with the concentration of orthophosphate above 0.01mg/L, the concentration of dissolved inorganic nitrogen under 0.1 mg/L, furthermore, the lower ratio of nitrogen to phosphorus was suggested to indicate the occurrence of the nitrogen fixing cyanobacteria, but the differentiation mechanism of nitrogen fixing and non-nitrogen fixing cyanobacteria need a deep research. Moreover, cyanobacteria nitrogen fixing rates can be influenced by the light availability, inorganic nitrogen concentrations, heterocyst abundance and the fixed nitrogen determines the contribution to the pools of nitrogen. The nitrogen fixing cyanobacteria is the important contributor to the pools of nitrogen in the ocean systems, but in the eutrophic lakes, its contribution is still in dispute. Thus, this paper reviewed the researches on nitrogen fixing cyanobacteria to attract attention of scientist on its important contribution to the pool of nitrogen in aquatic systems.