Abstract: A superoxide dismutase gene was cloned by differential screening of the subtracted cDNA library and RACE from Malus xiaojinensis Cheng et Jiang, which was named MxSod2 (Accession No. DQ431473). The full-length cDNA of MxSod2 is 805 bp, including the open reading frame (ORF) of 471 bp. It encodes a protein of 157 amino acids, with a molecular weight of 15 kDa. The MxSod2 contained the conserved domains shared in all known SOD. The phylogenetic tree suggested that MxSod2 was closer to the SOD of non-graminaceous plants including longan and litchi, but farther with the SOD of peanut, rice and maize.