Anionic water-dispersible copolyester was prepared by the polycondensation of dimethyl isophathalate (DMI)/5-sodium sulfo dimethyl isophathalate (DMS) with ethylene glycol (EG)/diethylene glycol (DEG) to synthesize water-dispersible copolyester-g-AA/EAs by chemical method. In the case of graft polymerization of AA/EA onto DMI/DMS/EG/DEG copolyesters, graft yield increases with increase in the AA molar feed ratio. Copolyester-g-AA/EAs dissolve completely in 1N aqueous NaOH solution whereas DMI/DMS/EG/DEG copolyester does not. This is a result of the core/shell structure that was ascertained by the graft yield and the zeta potential of copolyester-g-AA/EAs. It appears that grafted AA/EA exists at the surface of copolyester-g-AA/EA particles, and the backbone polymer, i.e., DMI/DMS/EG/DEG copolyester, exists in the inner phase of the copolyester-g-AA/EA particles. The complete solubility of copolyester-g-AA/EAs in 1N NaOH aqueous solution seems to come mainly from the electrostatic repulsion between - COOs that are present at the surface of copolyester-g-AA/EA particles due to AA grafting and - OHs that are present at the dispersion medium due to NaOH decomposition and which cause the hydrolytic breakage and consequently the coagulation of copolyesters in alkaline medium.