Starch-g-poly(2-methacryloyloxyethyl trimethyl ammonium chloride-co-acrylic acid) (starch-g-P(DMC/AA)) with different zeta potentials was prepared via the graft copolymerization of acid-thinned cornstarch (ATS) with 2-methacryloyloxyethyl trimethyl ammonium chloride (DMC) and acrylic acid (AA) in aqueous medium using Fe2+-H2O2 initiator. The investigation was carried out to reveal the influence of amphoteric branches grafted onto starch chains upon the adhesion of starch to textile fibers. Zeta potential of starch-g-P(DMC/AA) was adjusted by altering the mole ratio of DMC to AA charged into the copolymerization system. The adhesion was evaluated in terms of bonding strength and specific bonding strength of slightly sized roving based on a legal method (FZ/T 15001-2008) through the comparison of the amphoteric branch-grafted starch with ATS, starch-g-PAA, and starch-g-PDMC for warp sizing. It was found that the charged branches grafted onto starch chains were able to significantly enhance the adhesion. Zeta potential, depending on the mole ratio of DMC to AA units in the grafting branches, showed evident effect on the adhesion and desizability of the grafted starch. Increase in the potential favored to improve the adhesion, but disfavored the removal of the starch from sized warps. Alkali-oxidant agent desizing test confirmed that the starch-g-P(DMC/AA) with neutral potential was desizable. The amphoteric branch-grafted starch exhibited potential application as size base materials in warp sizing operation if its zeta potential was neutral.