Abstract: A large amount of nitrogen fertilizer is used in agricultural production. The excess nitrogen in the fertilizer flows into the water, causing high nitrogen concentration in the water, which has a great impact on the ecological environment. The controlling of nitrogen pollution in water is the key to the survival of modern agriculture. Biological denitrification has become a hot spot for removing nitrogen pollution in water due to its simple, efficient and stable features without secondary pollution. Denitrifying bacteria is the core of biological nitrogen removal technology. The research of new and efficient denitrifying bacteria is of great significance to the development of biological nitrogen removal technology. At present, more and more researches are conducted on denitrifying bacteria, including isolation and identification, influencing factors and practical applications of denitrifying bacteria.. The results show that, in the research of isolation and identification, the states of most denitrifying bacteria are colored circular colonies, which are basically bacillus; in the study of influencing factors, no matter for nitrifying bacteriaor denitrifying bacteria, the best temperature is between 30-35℃ , the optimal pH is neutral or weak acid and alkaline, and the optimal carbon-nitrogen ratio of the nitrifying bacteria is about 10, while the carbon-nitrogen ratio of the denitrifying bacteria is about 7. In the research of actual application, it is found that the denitrification effect of mixed bacteria is more obvious than that of single bacteria, however, the combination ratio needs to be further studied. The research of biological nitrogen removal technology is still in the laboratory stage, and screening more efficient strains, optimizing their nitrogen removal effects, and applying them to actual production will have important social value for the agricultural nitrogen pollution control in China.