Based on the EST sequence of mantle cDNA library of Hyriopsis cumingii, the complete cDNA of Hyriopsis cumingii GPX gene was cloned by rapid amplification of cDNA ends (RACE) in this paper. The GPX full-length cDNA sequence was 1286 bp including a 39 bp 5'-untranslated region, a 659 bp 3'-untranslated region and an open reading frame (ORF) 588 bp in length, which encodes for 195 amino acids with the predicted molecular weight of 22.2 kDa and the isoelectric point of 8.44. Molecular structure analysis revealed that GPX was Se-GPX. The amino acid sequences have three highly conserved loop structures that have a stabilizing effect on the tertiary structure of the enzyme. The amino acid sequence did not contain obvious hydrophobic domain and signal peptide. Homologous analysis of amino acid sequences indicated that the GPX of H. cumingii shared a high similarity with GPX-2 and GPX-1 of vertebrates (73.1%-80.8%), and low similarity with other types (lt; 60%). Phylogenetic trees showed that GPX of Hyriopsis cumingii was clustered together with GPX of some fishes and far away from GPX of several other published Molluscas. These results indicated GPX gene of H. cumingii cloned in this study was different from the GPX genes from other Molluscas.