A reusable chelating fiber containing polyamino-polycarboxylic acid ligands was prepared via the stepwise modification of polyacrylonitrile fiber with diethylenetriamine and chloroacetic acid. The amination and carboxylmethylation conditions were optimized, and the modified fiber was characterized by elemental analysis, XRD, SEM and FTIR. For Cd2+ in water, this chelating fiber has prominent adsorption abilities such as low adsorption limitation (0.001 mg/L), high adsorption capacity (1.34 mmol/g) and fast response speed (half-saturation adsorption time less than 0.5 min based on 1 mg/mL Cd2+). The effectiveness of this chelating fiber has been proved by using it to treat actual sewage water, where the concentration of Cd2+ was reduced from 0.540 to below 0.001 mg/L This level easily meets drinking water standards (0.003 mg/L) issued by the World Health Organization. Moreover, this chelating fiber is also very effective at treating other metal ions such as Cu2+, Ca2+, Zn2+, Mg2+, Ph2+, Ni2+, Ag2+ and Hg2+. (c) 2008 Published by Elsevier Ltd.