The kinetic parameters of chlorophyll fluorescence and the photosynthetic rate of the different genetic background flue-cured tobacco varieties (‘K326’,‘Yunyan 87’,and ‘Zhongyan 103’) were studied under different altitude conditions,and their influencing factors G_s,C_i,T_r,WUE were investigated.The result showed that:(1)There were positive correlation between the average daily value of P_n,G_s,WUE and altitude and negative correlation between the average daily values of intercellular CO₂ concentration (C_i),transpiration rate (T_r) and altitude.(2)The diurnal variation of P_n,C_i,G_s,and T_r in the leaves presented a one-peak distribution and an unobvious midday depression occurred at altitude of 1300 m,and the diurnal variation of P_n,C_i,G_s,and T_r presented a bimodal pattern and an obvious midday depression occurred in the sunny noon.(3)The primary light energy conversion of PSⅡ (Photo-systemⅡ) (F_v/F_m) and potential activities of PSⅡ(F_v/F₀) of the three tobacco varieties increased with increasing altitude.(4)The daily photosynthesis (∑P_n) of the three tobacco varieties increased with increasing altitude,and the daily photosynthesis of ‘Yunyan 87’ varieties were significantly higher than the other two varieties.At altitude of 900 m,flue-cured tobacco’s leaves had the highest daily transpiration (∑T_r),and the lowest in 1 300 m.Obviously,the photosynthetic characteristics and photosynthetic capacity of flue-cured were affected and restricted by altitude factors,and the photosynthetic characteristics of tobacco varieties should be considered during distribution of varieties.