γ-polyglutamic acid was produced by fermentation with bacillus natto screened from natto.Optimization of the fermentation medium by response surface method on the basis of single factor experiments was studied. Results revealed that the optimal medium constituents were as follows: sucrose 43.92 g/L, soy peptone 7.00 g/L, sodium glutamate 46.32 g/L. The production of γ-PGA increased from 7.253 g/L to 11.794 g/L．