Lactobacillus bulgaricus is a common yogurt starter in dairy production. But the viable counts of the bacteria in the productions are relatively low during free-drying and storage which is not good for its commercial production. In order to obtain a medium with high activity and high density for bacterial cultured, the experiments and regression analysis were conducted by Box-Behnken design in this study, and a model was established to predict the influence of glucose (9-11 g·L⁻¹), casein hydrolysate (15-17 g·L⁻¹) and glutamate (6.5-7.5 mg·L⁻¹) on viable counts of L. bulgaricus and. The results showed that the glucose, 9.5 g·L⁻¹; casein hydrolysate, 15.5 g·L⁻¹; glutamate, 7.0mg·L⁻¹, the number of viable bacteria of L. bulgaricus could reach (2.95±0.07) ×10⁹, which was very similar to the predicted value of the model of 3.00×10⁹ cfu·mL⁻¹, indicating that the optimized conditions and models used were feasible and effective. The optimized medium components can improve the viable counts of bacteria which are useful from its application in industrial production.