Abstract: A field trial was conducted to study the effects of different organic acids on maturity and quality of flue-cured tobacco. The results indicated that during ripe harvesting time, three organic acids could enhance K, reduce sugar contents, K/Cl, sugar/nicotine, and simultaneously reduce the protein and nicotine contents. But the effects of different kinds of organic acids were different. Malic acid and fulvic acid could obviously increase K content of the upper and middle stalk position leaves. Malic acid and oleic acid could obviously reduce the protein content of upper and middle stalk position leaves and nicotine content of middle stalk position leaves. During the over-ripe harvesting time, in comparison with the ripe harvesting time, chemical compositions of tobacco leaves were most coordinated in the fulvic acid processing, thus could improve the quality of tobacco leaves. The effects of fulvic acid were better than those of malic acid and oleic acid.