Abstract: Field experiment was conducted to study the effects of potassium sidedressing rates on growth, yield and quality of flue-cured tobacco, the results showed that, with the increase of potassium topdressing rate, potassium and total sugar content in leaves increased continuously, and nicotine content tended to decrease. There was significant correlation between potassium topdressing rate with nicotine, total sugar, reductive sugar, potassium content, sugar/nicotine, or nitrogen/nicotine, but no correlation with total nitrogen, chlorine, or potassium/chlorine. These were all presented that different potassium topdressing rate had a great effects on nicotine content, total sugar, potassium content, sugar/nicotine and nitrogen/nicotine of cured leaf, under the experiment condition, 1:1:3, the optimum ration of nitrogen: phosphorus: potassium supplied to the soil, was in favor of the maximum economic benefit and harmonious chemical components of cured leaves.