The extraction behavior of an alkaline protease using reversed micelles was investgated. The reversed micellar solution consisted of AOT in isooctane. It was found that distribution of arkaline protease into the organic phase increased at lower pH, lower ionic strength, and higher AOT concentration. When the real fermentation broth was extracted of alkaline protease, an activity yield of 20% and a purification factor of 2.0 were obtained.