Abstract:Cross-intron primers were designed according to the nucleotide sequence of the Actin of Phalaenopsis, and Actin homology fragments from Cymbidium sinense and C. goeringii were obtained by reverse transcription polymerase chain reaction (RT-PCR) and PCR using the first chain of cDNA and the genomic DNA as templates. The results showed that the Actin franments from C. sinense and C. goeringii were 1335 bp in length with 1086 bp coding sequences, encoding a protein of 362 amino acids. They were named as CsACT1 and CgACT1 (GenBank accession number were GU181354 and GU181353), respectively. Both of CsACT1 and CgACT1 consisted of three conservative introns. The amino acid sequence shared over 90% to those of other plants in the GenBank, so that the Actin genes from Cymbidium were highly conservative. The CsACT1 and CgACT1 could express at similar level in root, stem, leaf, pedicel, bud and floral organ, so that CsACT1 and CgACT1 might be constitutive expression Actin genes.