The flux of inorganic nitrogen flowing into the East China Sea was estimated based on the systematic analysis of all the pollution sources from 1980-2005. The result showed that the flux of inorganic nitrogen had been increasing from the early 1980s to the early 21st century. In detail, the flux was about 8.8 x 10(5) t x a(-1) in the early 1980s, and increased to about 2.6 x 10(6) t x a(-1) in the early of 21st century. The annual increasing rate was about 4.3%, and the mean flux was 1.8 x 10(6) t x a(-1). The flux of inorganic nitrogen of Yangtze River had also been increasing from early 1980s to the early 21st century. In detail, the flux was 4.0 x 10(5) t x a(-1) in the early 1980s, and increased to about 6.2 x 10(5) t x a(-1) in the middle 1980s, and was then kept at this value to the end of 1980s. After that, the flux value increased quickly from the early 1990s to 1.8 x 10(6) t x a(-1) in the early 21st century. Of all the sources, the proportion of land-source inorganic nitrogen was the largest, which was about 79%, among which, the river-source, the sewage-source and the non-point source accounted for 73%, 4% and 2%, respectively. Besides the land-source, the air-source and the mariculture-source accounted for 18% and 3%. The proportion of flux of Yangtze River in the river source was 76.5%.