Abstract: Objective To investigate the genetic characteristics of neuraminidase(NA) protein gene of the novel influenza virus A/H1N1 isolated in Henan province in 2009.Methods Thirty-five H1N1(2009) virus samples were isolated by laboratory of Henan Provincial Center for Disease Contorl and Prevention.After their RNA was extracted,we designed primers for reverse transcription(RT)-PCR to amplify the genes encoding NA protein.In the end,twenty NA genes were sequenced.We dow nloaded other sequences of NA gene of H1N1(2009) from NCBI database.Then the sequence alignment and the phylogenetic tree were constructed by using the MEGA4.1 softw are and NJ method.Results Two base mutation positions,316 G/A and 742 A/G,were found in the isolation of H1N1(2009).And other two mutation positions,945 A/G and 1338 T/C,were found in the isolation of H1N1(2009).The alignment showed that these mutation types were homologous to some sw ine flu NA gene sequences isolated from the swine infected human H1N1(2009).Conclusion The occurrence of the influenza A H1N1 NA gene's mutation had been proved during the first swine flu season in China.There was one change(regions 106 V/I) found in the influenza A H1N1 NA gene's antigenic regions.