A water-soluble sulfonated poly(aniline-co-o-anthranilic acid) were obtained from aniline and o-anthranilic acid through chemical polymerization method.Inhibition efficiency of this polymeric compound for mild steel in 1M hydrochloric acid solutions was investigated by weight loss measurements,potentiodynamic polarization and electrochemical impedance spectroscopy.Scanning electron microscopy and UVvisible spectra of poly(aniline-co-o-anthranilic) dissolved in HCl solution showed that the polymer was absorbed on the iron surface for corrosion inhibition.The polymer has show remarkable inhibition effect on the mild steel in 1M hydrochloric acid solutions.It is indicating that this polymer is an effective corrosion inhibitor.