Abstract: 【Objective】 To explore the effects of the auxin agar-coated controlled release simulation apical dominance method on the growth and upper leaf opening of flue-cured tobacco，which could provide theoretical reference for the efficient utilization of auxin in production to promote the growth and development of flue-cured tobacco and improve the availability of upper leaves. 【Method】 Yunyan 87，a flue-cured tobacco variety，was used as the experimental material. Agar blocks with auxin concentrations of 25 mg/kg（T1），50 mg/kg（T2）and 100 mg/kg（T3）were made，and agar blocks without auxin were used as control（CK），and the fixed auxin dosage was 0.5 mg/plant（except CK）. After topping，the agar block was covered on the wound of flue-cured tobacco stems. The photosynthetic parameters，root characteristics，leaf area，leaf opening degree and leaf metabolite content in the field，physical characteristics and economic benefits of flue-cured tobacco leaves after baking were measured in different treatments. And the correlation analysis was conducted on leaf area，leaf opening degree and photosynthetic characteristics，root characteristics of flue-cured tobacco leaves. 【Result】 The stomatal conductance of upper leaves treated with T2 and T3 were as 3.1 and 2.1 times as that of CK respectively，and both of them were significantly different from CK（P<0.05，the same below），which eased the stomatal limitation in the process of photosynthesis，significantly increased the net photosynthetic rate by 56.28% and 45.49% respectively. At the same time，T2 and T3 treatments also promoted root growth，with the root biomass and root activity significantly increased by 17.61% and 13.05%，55.50% and 32.57%，and the total leaf area significantly increased by 19.46% and 14.17% 30 d after topping respectively，and the average leaf opening degree of apper leaves in T2 treatment （31.45%）was significantly higher than CK（28.22%）. Correlation analysis showed that the total leaf area and average opening degree of the upper leaves of flue-cured tobacco were positively correlated with net photosynthetic rate，stomatal conductance，transpiration rate，root activity，total root length，total root surface area and total root volume，and the correlation reached a significant or extremely significant（P<0.01）level. After auxin agar coating treatment，the content of soluble sugars and free amino acids in the upper leaves decreased，while the content of starch and mineral elements（total phosphorus and total potassium）increased. Due to the growth of upper leaves，the physical properties of tobacco leaves after baking were obviously improved，the leaf tension value of T1-T3 treatments was significantly increased by 9.58% -10.78% compared with CK，the elongation at break and filling value of T2 treatment were significantly increased by 10.89% and 17.20% respectively compared with CK，the overall crushing resistance and looseness of tobacco leaves were enhanced，the proportion of high-grade tobacco leaves and field output value increased，and the economic benefits increased. 【Conclusion】 Using agar to coat auxin for controlled release，and then acting on the topping wound of flue-cured tobacco promote the growth and activity of root system of flue-cured tobacco，and increase the net photosynthetic rate by increasing stomatal conductance，thus promoting the growth of the upper leaves and their carbon and nitrogen metabolism processes，finally improving their physical characteristics and improving the economic benefits and availability of the upper leaves. The effect of treatment with auxin concentration of 50 mg/kg and content of 0.5 mg/plant is relatively effective.