Abstract: In this paper, the Cu2+ and Cd2+ binding properties of GmASR protein and its truncated polypeptides A1~A5 containing histidine were detected using immobilized metal ion affinity chromatography (IMAC). Then, the hydroxyl radicals reducing activities of GmASR protein and the polypeptides A1~A5 were determined by Cu-ascorbate system and it was found that the hydroxyl radicals reducing activities of GmASR and the polypeptides A1~A5 have a positive correlation with the number of histidine residues in their sequences. In addition, GmASR protein and polypeptides A1~A5 could protect DNA from oxidative damage caused by Cu2+.The results of CD and SDS-PAGE experiments indicated that Cu2+ binding to GmASR protein would cause reversible aggregation and precipitation of the protein and polypeptides in vitro. We speculate that GmASR can bind excess metal ions in the cytoplasm by means of the histidine-rich motifs and maintain intracellular ion balance and protect plants from heavy metal toxicity.