The potato phosphorylase-catalyzed polymerization of alpha-D-glucose-I-phosphate (G-1-P) onto poly [styrene-block-(4-vinylbenzyl maltohexaoside)] (1) was performed at the molar ratios of [G-1-P](0) and [maltohexaose](0) of 35, 80, and 250. The product was found to be soluble in dimethyl sulfoxide, which was a good solvent for amylose, and showed the complex-formation with iodine, indicating that the product was assignable to poly[styrene-block-(styrene-graft-amy lose)] (2). The quantitative analysis of the liberated phosphoric acid gave the average degree of polymerization of the glucose unit (n) as 27, 51, and 180 for 2-I, 2-II, and 2-III, respectively.