Abstract: To confirm the photosynthetic physiological mechanism of growth and quality variance formation of the flue-cured tobacco leaves in different stalk positions, the photosynthetic characteristics of the flue-cured tobacco leaves in different stalk positions and environmental factors that affect photosynthesis were discussed. Taking‘Yuyan 10’as the materials, the photosynthetic characteristics and environmental factors diurnal variation process of the flue-cured tobacco leaves in different stalk positions were determined in the fast grow stage, and path analysis method was used to analyze the direct and indirect effects of environmental factors on the net photosynthetic rate (Pn). The results indicated that: (1) the Pn diurnal variation of the leaves in different stalk positions were‘unimodal type’. The Pn daily average values of the upper, middle and lower leaves were 13.25, 11.71, 6.26μmol CO₂/(m²·s) and the value of the lower leaves was significantly lower than the upper and middle leaves. (2) Stomatal conductance (Gs) had greater influence on flue-cured tobacco transpiration than the photosynthesis. With the increase of the Gs, the Pn and the transpiration rate (Tr) of the flue-cured tobacco leaves in different stalk positions showed ascendant trend. Overall, the peak time of the blade Tr and Gs was consistent, while they both lagged behind the peak time of Pn. (3) The main decision variables of the flue-cured tobacco leaves in different stalk positions were the photosynthetic active radiation (PAR) and the main restriction variables were the atmospheric temperature (Ta). Therefore, to improve the Pn of the fluecured tobacco leaves in different stalk positions, certain measures such as reducing the planting density needed to be taken to increase the PAR appropriately and control the microenvironment Ta, thereby improving the various parts of the blade temperature (Tl). Keeping atmospheric CO₂ concentration (Ca) basically constant was also necessary.