Response surface methodology was used to optimize the medium for antifungal active substance production from Streptomyces lydicus E12 in flask cultivation.Initially,the component factors,which influence antifungal substance production,were studied by varying one factor at a time.Starch,soybean cake powder,K_2HPO_4·3H_2O and MgSO_4·7H_2O were found to have a significant effect on the production of antifungal substances by the traditional design.Then,a Box-Behnken design was applied for further optimization.A quadratic model was found to fit antifungal active substance production.The analysis revealed that the optimum values of the tested variable were starch 84.96 g/L,soybean cake powder 4.13 g/L,glucose 5 g/L,MgSO_4·7H_2O 1.23 g/L,K_2HPO_4·3H_2O2.14 g/L and NaCl 0.5 g/L.The test result of 67.44%antifungal inhibition agreed with the prediction and increased by 14.28%in comparison with the basal medium. Response surface methodology was used to optimize the medium for antifungal active substance production from Streptomyces lydicus E12 in flask cultivation. In component, the component factors, which influence antifungal substance production, were studied by varying one factor at a time. Starch, soybean cake powder, K 2 HPO 4 · 3H 2 O and MgSO 4 · 7H 2 O were found to have a significant effect on the production of antifungal substances by the traditional design. Chen, a Box-Behnken design was applied for further optimization. A quadratic model was found to fit antifungal active substance production. The analysis revealed that the optimum values ​​of the tested variable were starch 84.96 g / L, soybean cake powder 4.13 g / L, glucose 5 g / L, MgSO 4 · 7H 2 O 1.23 g / L, K 2 HPO 4 · 3H 2 O 2 · 14 g / L and NaCl 0.5 g / L. The test result of 67.44% antifungal inhibition agreed with the prediction and increased by 14.28% in comparison with the basal medium.