An investigation was undertaken to develop a new method to obtain fine dispersion of grafted polyester without gelation. As a new method, grafting utilizing alternating copolymerization of hydrophilic polymers to unsaturated polyester was discussed. By use of grafting utilizing alternating copolymerization, the reaction tendency of grafted polymer radical for an unsaturated bond of the polyester was changed. The grafting utilizing alternating copolymerization was compared with the conventional grafting, and the calculated grafting efficiency is about twice. Moreover, it was possible to increase the incorporation of less reactive monomers into the grafted side chain by the grafting utilizing alternating copolymerization. From the above results, the grafting utilizing alternating copolymerization is considered a useful method to prepare grafted polymers.