Selenocysteine methyltransferase (SMT) is a key enzyme of selenium metabolism pathway in plants and plays important roles in accumulating for selenium in plants. To investigate the function of SMT in Dioscorea Esculenta (Lour) Brukill, the full-length cDNA was cloned from Dioscorea Esculenta (Lour) Brukill Ds148 using reverse transcription-PCR (RT-PCR) technique. This gene was named DsSMT with a GeneBank accession number MH046782. The full-length open reading frame (OFR) of DsSMT was 1038bp that encoded 345 amino acids. The predicted molecular weight is 37.24 kD with the hypothetical isoelectric point of 5.01. DsSMT was highly conserved and grouped with the homologous proteins from Phoenix dactylifera and Ananas comosus. Wolf Psort protection indicated that DsSMT protein was located in cytoplasm. Real-time quantitative PCR (RT-qPCR) analysis revealed the transcripts of DsSMT in different tissues of Dioscorea Esculenta (Lour) Brukill, including roots, stems, leaves, tubers and the peel of tubers. The levels of DsSMT were different among different tissues, and the level was the highest in roots and mature period during the process of Dioscorea Esculenta (Lour) Brukill development, respectively. Furthermore, the expression level of DsSMT was obviously down-regulated during the enlargemental period, and then increased during the mature period. These results isolated the coding sequence of DsSMT gene and unlocked its expressional profiles, which provided a base in future study of molecular regulation mechanism on selenium metabolism in Dioscorea Esculenta (Lour) Brukill.