[Objective] In order to improve the acetoin production efficiency by Bacillus subtilis CCTCC M 208157. [Methods] The processes of acetoin fermentation were investigated under various pH conditions in a 7 L fermentor. [Results] The effects of pH on cell growth and acetoin production showed that the optimum pH for acetoin production and cell growth were 4.5 and 5.5, respectively. Based on the above results, a two-stage pH control strategy was developed: the pH was controlled at 5.5 for the first 16 h, and then decreased to 4.5 for the remaining time. [Conclusion] With this optimized pH control strategy, the production of acetoin had a significant improvement. Moreover, the production, conversion rate from glucose and productivity of acetoin were achieved at 32.7 g/L, 0.41 g/g and 0.91 g/(L·h), respectively, which were 41%, 42% and 69% higher than that from the strategy without pH control.