Accumulation of dry matter, absorption and distribution of fertilizer nitrogen and soil nitrogen and the effects of fertilizer nitrogen and soil nitrogen on quality of flue-cured tobacco leaves were studied by ¹⁵N-labelled field trial on paddy soil. The experiment was carried out simultaneously in two fields at Zhaowei Village Group 6 and Zhaowei Experiment Base respectively, in Hongta District, Yuxi City, Yunnan Province, China. There were two treatments in each field: without applying fertilizer nitrogen and applying fertilizer nitrogen 90 kg/ha. The results indicated that applying fertilizer nitrogen remarkably increased dry matter and nitrogen content of flue-cured tobacco. However, both accumulation dry matter and absorption nitrogen were excessive in latter growth period. In the treatment of using nitrogen 90 kg/ha, most nitrogen of tobacco plants derived from soil, and soil nitrogen content and the ratio to total nitrogen evidently increased with growth period extending and stalk position ascending. The ratio of soil nitrogen to total nitrogen was respectively up to 0.69 and 0.74 at the end of growth period in Group 6 field and Experiment Base field. The experiments also showed that the content of nitrogen and nicotine of leaves were lower than the contents of high quality tobacco leaves, and the ratio of nitrogen to nicotine was lopsided under the condition of without applying fertilizer nitrogen. The content of nitrogen was appropriate, but the nicotine concentrations of upper leaves were too high for the excessive supplement of soil nitrogen at fertilizer nitrogen rate of 90 kg/ha. The study suggests that it is important to choose soil with appropriate organic matter concentration to plant tobacco and control soil nitrogen supplement amount in latter growth period for reducing nitrogen and nicotine concentration of upper leaves and improving the overall quality of China's flue-cured tobacco.