The effects of aeration, agitation speed and pH on polyphenol oxidase production by Coriolus versicolor using a jar fermenter were examined. The optimum culture conditions were determined to be an aeration rate of 0.5 vvm, an agitation speed of 400 rpm, and pH control at 4.0. By optimizing the culture conditions, the dry weight of mycelia increased to 19.1 mg/ml in 5 d, and the enzyme activity reached 10.5 U/ml in 7 d.