To clarify structural characteristics of the gene encoding sulfite oxidase (SO) and its expression property in the development of various organs in maize,we cloned the fulllength cDNA of SO by RACE.Sequence analysis has shown that the cDNA of ZmSO is 1 492 bp,which contains the 160 bp of 5′UTR，138 bp of 3′UTR,and a 1 194 bp open reading frame (ORF).The structure prediction indicated that ZmSO contains one Mocobinding domain,one dimerization domain and one peroxisome targeting signal.Phylogenetic tree of SO based on different species has demonstrated that ZmSO has quite high similarity with SO from other plant species.Quantitative realtime PCR has revealed that the ZmSO transcript levels were higher in aerial organs of maize including stems,leaves,silks and immature ears,especially in leaves and immature ears,but the lowest in roots.Moreover,the distribution status of SO activity in the six organs is similar to that of their mRNA abundance.