The genetic engineering strain with recombinant plasmid pET-28a-pam was expressed in E.coli BL21. The fermentation conditions of initial pH, shaking speed, inoculation time and fermentation time were optimized with the PAM activity by using single factor. The results showed that the optimal fermentation conditions were initial pH 7.0, 200 r/min, the tenth hour broth and liquid volume 50 mL/500 mL, fermented for 24 h. Furthermore, the three factors were optimized by Box-Behnken design, and the results showed that inoculation time, initial pH and fermentation time are main affecting factors and their optimal levels are 12.8 h, 6.7 and 25.2 h. Under the optimal conditions, th activity of PAM reached 11.15 U/mL, improved by 128.9% compared with that under initial culture conditions.