Abstract: The fermentation of Lysobacter enzymogenes OH11 was investigated through single-factor test. The main factors include: temperature, rotate speed. The optimal fermentation conditions are: temperature 30℃, rotate speed 150 r/min. The orthogonal experiment was used to optimize the medium, and the microbe number of OH11 could reach 4.5×10⁹ cfu/ml under optimal condition after 48 h. The fermentation condition of OH11, such as volume, fermentation time, inoculum's size and pH value before sterilization were tested by orthogonal experiment. The optimum fermentation conditions are as follows: volume 40 ml/250 ml, fermentation time 72 h, inoculum size 10⁸ cfu/ml, pH7.5 before sterilized.