Abstract: This paper describes the preparation and properties of polymer-supported liquid membrane-immobilized cells of Arthrobactcr simplex which catalyze the transformation of cortisol into prednisolone.The transforming activities of cells immobilized by this method was compared with that of cells immobilized by traditional entrapment method.The results showed that the former were obviously higher than those of the latter,and there was nosapprent difference of mechanical strength between the former and the latter on our operational conditions.The various factors affecting the transformation were studied as well.