Abstract: Non-single organic solvent,methanol-ethanol fractional precipitation method was applied to extract γ-polyglutamic acid( γ-PGA) from the fermentation broth,meanwhile the extraction conditions were optimized by response surface method. Also the effects of organic solvent precipitation multiple,pH and time on the γ-PGA purity were observed through Box-Behnken design( BBD) on the premise of preliminary consideration of single factor. The results under Design-Expert v8. 0. 6. 1 software showed that the obtained optimal extraction conditions were the combination of organic solvent precipitation multiple 3. 48,pH 8. 13,and 7. 30 hours. Under the optimum extraction conditions,the corresponding values of purity and extraction ratio of γ-PGA were 75. 16% and 88. 73%,respectively. The predictive accuracy was 99. 02%.