Abstract: In order to clarify the physiological mechanism of tobacco suffered aluminum toxicity in acidic soil,the effects of aluminum stress on the growth and photosynthetic characteristics of flue-cured tobacco were studied via hydroponics experiments at 4 aluminum sulfate concentrations,0,50,250 and 500 μmol·L^-1,with the nutrient solution pH of 5.0.The results showed that:1) The root vigor of tobacco decreased obviously.2) The fresh weight,dry weight of roots and the biomass of stems and leaves decreased with the increase of aluminum concentration,and the root was affected more than stems and leaves.3) Under aluminum stress,the plant height,stalk circumference and single leaf area were inhibited;however,leaf length was not affected obviously,while leaf width did,which resulted in narrow long leaves.4) The content of chlorophyll in leaves increased significantly 5 days after aluminum stress,but the influence became unobvious 20 days after aluminum stress.5) The net photosynthetic rate,stomatal conductance and transpiration rate of tobacco leaves increased at 50 μ mol·L^-1,while significantly decreased at 250 and 500 μmol·L^-1.However,aluminum stress did not remarkably affect the intercellular CO₂ concentration of tobacco leaves.