Abstract: To investigate the contents of TSNAs in lamina and midrib of flue-cured tobacco stored under natural conditions and to establish effective ways to reduce TSNAs, flue-cured tobacco samples collected from different tobacco-planting areas were stored under natural conditions. A controlled experiment for varying moisture contents in tobacco leaves was conducted. The contents of TSNAs and their precursors in lamina and midrib of flue-cured tobacco were determined before and after natural storage. The results showed that after storing for one year, the contents of TSNAs in lamina and midrib of flue-cured tobacco significantly increased. The proportion of increase for TSNAs in midrib was significantly higher than those in lamina, at 5.78 times higher. The nitrate contents in lamina and midrib significantly reduced, and the decrement in midrib was 32.23 times of that in lamina. The alkaloids contents in lamina and midrib were also reduced, however the variation was not significant. Correlation analysis indicated that the increase proportion of TSNAs in lamina significantly positively correlated to nitrate content. After storing in vacuum for one year, the linear correlation was observed between TSNAs content and moisture content. TSNA contents decreased with the increase (from 6.8% to 23.1%) of moisture content in tobacco leaves. Therefore, reducing TSNAs precursor contents and appropriately increasing the moisture content in tobacco leaves were beneficial to reducing the formation and accumulation of TSNAs during natural storage.