Graft copolymerization of acrylic acid ( AA) onto starch was carried out with ceric ammonium nitrate as initiator under nitrogen atmosphere. The structures of the synthesized graft copolymers were identified by Fourier transform infrared ( FTIR) spectroscopy and scanning electron microscopy (SEM). The grafting percentages (GP%) of starch-graft-acrylic acid (S-g-AA) copolymers were determined. Increasing the molar concentration of AA from 0.1 to 0.5 mol/L caused a significant increase in the GP%. The effect of GP% of S-g-AA copolymers on the competitive removal of Pb2+, Cu2+, Cd2+ ions from aqueous solution was investigated at pH 4.5. The concentrations of each ion in aqueous solution were equal to each other, which were kept constant at 4 mmol/L. Metal ion removal capacities were determined by atomic absorption spectrophotometer (AAS). Metal ion removal capacities of S-g-AA copolymers rose with the increase in GP% of the copolymers and the order of the removal of heavy metal ions was Pb2+> Cu2+> Cd2+.