Abstract: A total of 111 samples in 2011 and 2012 was collected to study the variation of chemical constituents of various years， different grades and different cultivars of burnt\|sweetness type flue\|cured tobacco of Hunan. The results showed that the total sugar， reducing sugar， sugar\|alkali ratio and potassium\|chloride ratio of tobacco leaves in 2012 were higher compared with 2011. Total nitrogen nicotine， potassium， chloride， starch and nitrogen\|alkali ratio decreased. Differences in chemical constituents were significant or extremely significant among grades. Variation trend of 2011 and 2012 was basically the same. Total sugar， reducing sugar， potassium， sugar\|alkali ratio， nitrogen\|alkali ratio， potassium\|chloride ratio varied as follows: X2F>C3F>B2F；and total nitrogen， nicotine， chlorine showed as: B2F>C3F>X2F. The same chemical composition did not change significantly between different varieties.

Key words: flue\, cured tobacco, chemical constituents, burnt\, sweetness type