Abstract: In order to obtain the nitrogen concentration in mainstream lower Yangtze river and provide basic data for controlling nitrogen pollution, in June 2014 we detected the concentrations of TN,TDN and NH₄⁺-N in surface, middle and bottom water of lower Yangtze River, and analysed the spatial distribution characteristics of nitrogen. Results reveal that TDN is the main form of nitrogen in the mainstream of lower Yangtze River, and the concentration of nitrogen varies with the depth of water. The range of TN concentration was 0.85-2.46 mg/L and the average concentrations of TN in surface and bottom waters were higher than that in middle water. The range of TDN concentration was 0.72-2.08 mg/L, and the average concentration of TDN in surface was much higher. The range of NH₄⁺-N concentration was 0.13-0.75 mg/L, and the average contents of NH₄⁺-N were similar from the bottom to the surface waters. The average contents of TN and TDN present ascendant trend, and the average content of NH⁴+-N varies greatly between different cities from upstream to downstream in the study area. Through correlation analysis we also found that TDN is in significant negative correlation with chlorophyll-a (Chl), water temperature (T) is significantly positively correlated with chlorophyll-a (Chl), but the other forms of nitrogen have no obvious correlation with water’s physicochemical property.