The physiological and biochemical traits of flue-cured tobacco leaves under different humidity during curing were studied. The results showed that the higher amylase activity with faster degradation of starch was found in the low humidity treatment in the first 48 hours of curing, subsequently in the high humidity treatment, with the lowest starch content ultimately. The activity of PPO was the lowest in the low humidity treatment followed by the mid-humidity and high humidity subsequently in the first 48 hours of curing, whereas reached the peak level after 72 hours of curing. The decreased membrane lipid peroxidation was observed in the high humidity treatment, and no evident degradation of chlorophyll appeared in all treatments. The high humidity treatment was favorable for balance of chemical components, yet with relatively poor sensory quality. The most favorable sensory quality was found in low humidity treatment, while the best appearance quality and economic character were observed in mid-humidity treatment.