Abstract: The effects of the temperature,humidity and duration of yellowing stage during flue-curing on the respiration rate of and the contents of routine chemical components and neutral aromatic components in upper leaves were studied.The results showed that there were two peaks of respiration rates at different temperatures,humidities and durations,the first peak appeared at the 44th hour and the second appeared between the 64th and the 68th hour during curing.Continuous treatment for 24 hours at a dry bulb temperature of 40-42℃ and a wet bulb temperature of 37.5℃ was favorable for maintaining a high respiration rate,it promoted chemical transformations,the decrease of starch content and increase of neutral aromatic component contents in upper leaves.