The effects of soil and climate on nicotine and potassium content of cured tobacco leaves were studied through a field plot experiment with soils from Weining, Kaiyang and Tianzhu with obvious different ecological regions in Guizhou Province, and using flue-cured variety of Yunyan 87 as the test materials. Results showed the influence degree of different ecological factors on nicotine and potassium content of cured tobacco leaves was distinctly different. The effect of climate on nicotine content of cured tobacco leaves was higher than that of soil. The variability of nicotine content among climate factors was almost 4 times higher than that among soil factors. The contributing rates of climate and soil to the variation of nicotine content were 47% and 18%, respectively. The cumulative rainfall at maturing stage and ≥10℃ accumulated temperature at maturing stage, the amount of sunlight hours at the earlier growing stage in field were the top three climate factors affecting nicotine content of cured tobacco leaves. The effect of soil on nicotine content of cured tobacco leaves was obviously higher than that of climate. The variability of potassium content among soil factors was 1.5 times higher than that among climate factors. The contributing rates of soil and climate to the variation of potassium content were 40% and 14%, respectively. The available potassium content, organic matter content and total nitrogen content were the top three soil factors affecting potassium content of cured tobacco leaves. The effect of climate on nicotine content could not be neglected when the nicotine content was regulated by varieties distribution and agronomic measures. Soil factors should be mainly considered in order to improve potassium content of tobacco leaves.