A full length cDNA of Cu/Zn-SOD was firstly cloned in sandworm Perinereis aibuhitensis by homology cloning and RACE techniques based on the partial copper-zinc superoxide dismutase ( Cu/Zn-SOD) gene from pol-ychaete Alitta succinea. The full length of the cDNA was found to be 870 bp including a 156 bp 5′untranslated re-gion,a 261 bp 3′untranslated region and 453 bp open reading frame encoding 150 amino acids. There were typical Cu2+ and Zn2+ binding sites as well as two Cu/Zn-SOD protein family tag sequences in the deduced protein which was within the intracellular Cu/Zn-SOD with relative molecular mass of 15 249 900 and the isoelectric point of 5. 66 by bioinformatic analysis. No signal peptide and transmembrane domain were observed in the deduced pro-tein, indicating that it belonged to the hydrophilic protein. Multiple sequences alignment analysis revealed that the deduced amino acids had high homology to the proteins of partial molluscs, fishes and insects. The findings will provide basis for research of dose-response between gene expression and environmental pollutants, and defense mechanism of the sandworm.