ACC oxidase (ACO) gene plays a critical role in regulating the biosynthesis of ethylene,which is a phytohormone that shortens the longevity of orchid flowers. The present study was carried out to clone cDNAs encoding the senescence-associated ACC oxidase gene from Dendrobium sonia cultivar ‘Earsakul’ flowers, DsACO, and to compare the DsACO with the ACO from D. sonia, Dendrobium hybrid cultivar‘Anna’ and D.crumenatum. Cloning of the ACC oxidase gene from the cultivar ‘Earsakul’, DsACO, was performed by RT-PCR and the nucleotide sequence analysis of this gene revealed that the open reading frame of the gene was 972 bp in length, encoding 323 amino acid residues. The PCR productwas cloned into pDRIVE vector, transformed into the bacterium Escherichia coli strain DH5α,and the nucleotide sequence of the DsACO was characterized and compared with the ACO from seven orchid species available in the GenBank database. The BLAST results manifested that the DsACO shared high similarities of 98.9, 96.2 and 90%,respectively, with the ACO from the cultivar ‘Anna’, D. sonia and D. crumenatum, indicating that the DsACO was successfully cloned into the pDRIVE vector.