Abstract: Objective To investigate the genetic characterization(evolution,antigenicity,enzymatically active site and glycosylation site) of the neuraminidase(NA) gene of the pandemic influenza virus A(H1N1) in Shandong province.Methods Genetic evolution and amino acid substitutions of the 20 NA gene sequences of pandemic influenza virus A(H1N1) isolated in Shandong province were analyzed with MEGA 4.0 software.Results The pandemic influenza A(H1N1) viruses shared a homology of more than 99.2%.Phylogenetic analysis for neuram in idase showed that the strain related to the vaccine strain(A California 07-2009H1N1) and the reference strain in China(A Sichuan 1-2009H1N1), with 99.1%-99.5% and 99.1%-99.6% of sequence identity, respectively.The NA amino positions were changed at 21, 23, 25, 42, 43, 60,76, 94, 106, 122, 248, 307, and 351.No mutation of 275 in NA protein was found.Conclusion The NA gene of the pandemic influenza A(H1N1) virus in Shandong province were highly homologo u.s Amino acid residue sat the enzym atically active sites and the glycosylation sites was strictly conservative in all influenza virus strains.All the samples are sensitivity to oseltamivir.