A strain producing neutral protease was obtained from soil by diluted plated method and was named BX-4. Optimal fermentation medium was obtained through studying carbon resources, nitrogen resources and implementing orthogonal experiment. The effects of initial pH, metal ions and inoculum amount on protease production and the effects of temperature,pH surface-active agent on protease stability were studied. Protease activity reached 2 519.35 U/mL under the conditions of 37 ℃,160 r/min ,48 h in the optimal f...