6 neutral protease strains was screened from the soil, among which a highest enzyme producing strain bacillus subtilis was studied on its optimum neutral protease producing conditions by fermentation. The results showed that the optimum culture medium was prepared with corn flour of 1%, (NH4)2SO4 of 0.6%、Na2HPO4o12H2O of 0.4％, KH2PO4 of 0.03％, CaCl2 of 0.1％, pH of 6.0. And the optimum neutral protease producing conditions were as follows: fermentation time 48h, fermentation temperature 30℃, the loaded crude enzyme solution 100mL/250mL. In these conditions, the highest enzyme activity of crude enzyme reached 1475.6U/mL.