An attempt to enhance the transglycosylation activity of lysozyme was made by chemical modification. Computer simulation of the lysozyme-catalyzed reaction indicated that inhibition of the sugar residue binding to the binding subsite A caused a significant increase in transglycosylation activity. Therefore, the binary modification of Asp 101 and Trp 62 in hen egg white lysozyme was made in order to inhibit the sugar residue binding to subsite A. The modified lysozyme, in which the affinity of the sugar residue to subsite A was decreased by about 2kcal/mol of binding free energy change, increased the amounts of transglycosylation products in comparison with the native lysozyme. In particular, the octamer of N-acetylglucosamine was abundantly produced from the initial substrate, pentamer. The modified lysozyme should be useful for synthesis of oligosaccharides with a high degree of polymerization.