Cloning of the DenACO from Dendrobium hybrid cultivar Anna was performed by RT-PCR and nucleotide sequence analysis revealed that the open reading frame of this gene is 942 bp long, encoded for a protein of 313 amino acid residues. The calculated molecular mass of the deduced polypeptide is 35.6 kD and the predicted isoelectric point is 4.19. The deduced amino acid sequence of the DenACO-encoded protein showed a high degree of identity to those of the ACO from rose, geranium, carnation and tulip. RT-PCR analysis of gene expression revealed that the DenACO was expressed during the stage of flower development and in all floral tissues including petal, sepal, pedicel, larbellum and stigma. In addition, the higher expression of the DenACO was observed in leaf of the orchid plants as compared to the root. These results suggested that the orchid DenACO plays a crucial role in the flower development process.