A starch degrading bacterium HX-6 was isolated and screened from the surface of Henan flue-cured tobacco leaves, and the enzyme-producing medium and tobacco fermentation process of the strain were optimized. The results showed that starch degrading bacterium HX-6 was identified as Bacillus subtilis, and the optimum enzyme-producing medium formula was as follows: 17.0 g/L soluble starch and sweet potato starch (m _{soluble starch}∶m _{sweet potato starch}=1∶1), 21.89 g/L peptone and yeast powder (m _peptone∶m _{yeast powder}=1∶1), 2.58 g/L KNO₃. The enzyme activity of HX-6 was increased by 71.51%. The optimum tobacco fermentation process was found to be using 4% crude enzyme solution of HX-6 strain and fermenting at 35 ℃ for 27 h. After fermentation, the starch degradation rate reached 31.75%, and the total sugar and reducing sugar content increased by 18.8% and 20.2% respectively. The sensory quality was significantly improved (P<0.05), and the aroma quality became better, with the increase of aroma volume.