Abstract: In order to improve the α-amylase production activity of genetically engineered strain BAX-5/PT-17 SP002amy(A8-1), improve its industrial applicability and application effect in tobacco processing, a series of parameters in the fermentation process were optimized through single factor test and response surface experiments, and the scaled-up process was validated in a fermenter. Meanwhile, changes in chemical composition and sensory quality of tobacco with α-amylase treatment were analyzed. After optimization, the optimal fermentation medium and conditions for strain fermentation were determined as: corn meal 65 g/L, soybean cake meal 70 g/L, NaCl 10 g/L, CaCl₂ 3 g/L, fermentation time 52 h, temperature 40 ℃, pH 6.0, inoculation volume 3%. The optimized α-amylase activity reached 1880.1 U/mL. Compared with 30.6 U/mL before optimization, the enzyme activity increased by 61.4-fold changes, and the enzyme activity could achieve 2276.2 U/mL in 5 L fermenter. After 7 U/g α-amylase treatment, the starch content of tobacco decreased by 19.9%, the total sugar and reducing sugar content increased by 8.09% and 7.81%, respectively. The aroma precursor substances and other indicators were positively improved in varying degrees. The treated tobacco exhibited enhanced aroma richness, smoother and milder smoke, with reduced irritancy and off-notes. The optimized fermentation process significantly improved the enzyme yield of genetically engineered strain A8-1, demonstrating strong industrial application potential. Its implementation in cigarette production effectively modifies chemical composition and elevates smoke quality.