Abstract: Yunyan 87 was taken as the test material. Agar blocks containing IAA were applied to topping wounds after topping, with treatments designated as CK, T₁, T₂, and T₃(CK:agar block without IAA; T₁:agar block containing 25 mg/g IAA; T₂:agar block containing 50 mg/g IAA; T₃:agar block containing 100 mg/g IAA). This study investigated the effects of different treatments on endogenous hormone metabolism and maturity tolerance in upper leaves of flue-cured tobacco. The results showed that T₁, T₂, and T₃ significantly increased IAA content in the upper leaves of flue-cured tobacco and brassinolide(BR) content BR at the later stage of topping, inhibited ABA synthesis, increased the ratios of growth-promoting hormone to ABA, enhanced superoxide dismutase and peroxidase activities(POD and SOD), thereby delaying the decline rates of cell membrane stability index(MSI) and SPAD values. Thus, the application of agar-coated controlled-release IAA to topping wounds delayed leaf senescence, and ultimately improved field maturity tolerance, with the T₂ treatment demonstrating the most optimal effects.