A strain named P3-2 with the ability to produce protease was isolated from castor bean meal and laboratory preservation by the casein plate culture method and enzyme activity detection. The optimal fermentation conditions were investigated. The optimum carbon and nitrate sources were maltose and castor bean meal. Meanwhile, the yield of protease was increased by adding Na⁺ and one peak of the protease yield was obtained when the initial pH value of medium was 7.5. Moreover, the optimum amount of inoculum was 4% and there were two peaks of the protease yield when culture time was 36 h and 84 h. Through the orthogonal experiment, the optimum compositions of medium were as follows:2.0% maltose, 1.0% castor bean meal, and 1.0% NaCl.