The amphiphilic copolymer, polyalkylene oxide allyl ester - maleic anhydride copolymer was used to modify the lipase from canadida cylindracea. The modification reaction, maleylation coours easily and effectively because maleic anhydride is very reactive chemical. The degree of modification (DM) was varied by changing the weight ratio of copolymer to lipase over the range of 0.5 ~ 4 (w/w). The relative activity decreased as DM increased. The specific activity of modified lipase was about 2 ~ 4 fold of that of native lipase in the severe pH and temperature condition.