Abstract: Currently, high sugar and low nicotine contents in flue-cured tobacco leaves in Yanbian area had resulted in some problems. A field experiment with the Jiyan 9 was carried out to investigate the effects of various root cutting treatments on tobacco root growth and leaf sugar, nicotine, potassium content. The results showed that root cutting obviously promoted the tobacco root growth, improved root activity at later growth stage of tobacco, and also increased the uptake of the nutrition of tobacco. Root pruning reduced sugar of tobacco leaves, improved the nicotine content, and increased the K content of middle and upper leaves, and harmonized the chemical components. In general, through the rosette stage light root pruning, root activity was significantly higher than other treatments in later growth stage, and increased the nicotine and potassium content, and reduced sugar content of tobacco leaf appropriately, and the ratio of sugar and nicotine was more coordinaed, which improved the internal quality of tobacco leaves.