Total RNA of influenza A virus(H5N1)was isolated by treatment of aliquots of the virus with TRIAZOL.Full-length NA cDNA was prepared by RT-PCR and cloned into pMDT-18 vector.Sequence analysis proved that the cloned NA gene of the Pigeon H5N1 Influenza A virus consisted of(1 350 bp) nucleotides and encoded a polypeptide of 449 amino acids residues.When compared with other influenza a virus(H5N1) in China,it showed a homology of 77.6%～98.8% at the nucleotide level and 77.6%～99.1% at the amino acid level.