Abstract: In order to improve the quality of upper tobacco leaves， proteins in tobacco leaves were degraded by flavored proteinase， and the physical structure， free amino acids， aroma component of the processed tobacco leaves were compared with the control. The protein content decreased by 191% after proteinase degradation， and the texture of tobacco leaves became loose. The sensory characters were improved due to increased aroma， lightened miscellaneous odors， lowered irritation， and cleaner aftertaste. Especially， the bitterness and pungent taste was obviously eliminated. Besides， the content of free amino acid and aroma significantly increased. The above results indicated that flavored proteinase degradation was effective to improve the smoking quality of upper tobacco leaves.

Key words: flue\|cured tobacco, flavored proteinase, physical structure, free amino acids, aroma component