Copolymer consists of polyethylene oxide (PEO) and maleic acid anhydride (MA) was used to modify the lipase. By controlling the ratio of ethylene oxide to alkylene oxide (AO), hydrophilic property of copolymer was controlled and the MA functional group of copolymer covalently coupled with the amino groups of lipase. Activity of modified lipase increase more than native one by about 20 ~ 30% due to substrate effect of synthesized copolymers. Native lipase was absolutely specific that only reacts limited substrate. However, as the modification was progressed, lipase was changed to group specificity that widely reacts several substrates having similar characteristic.