Abstract: To study the genetic variation and evolutionary characteristics of H1N1 Swine Influenza Virus (SIV), nasal swabs samples of pigs with influenza-like clinical symptoms were collected from Henan Province in 2010. Influenza virus was isolated by SPF embryonated eggs and identified by HA, HI test and RT-PCR methods, NA gene was amplified and genetic evolutionary analysed. The result showed that a H1N1 influenza virus was isolated and designated A/swine/Henan/405/2010(H1N1) (SW/HN/405/10). Homology analysis founded the SW/HN/405/10 showed a high sequence homology with avian-like SIV (92.1%-99.4%) and a highest homology with A/swine/Hong Kong/NS62/2005; Sequence analysis showed that amino acid residues at the enzymatically active site, glycosylation sites and disulfed bonds were strictly conserved, but the antigen sites varied. Phylogenetic analysis showed that SW/HN/405/10 was clustered in the same groups as the avian-like H1N1 SIV. These results indicated that the NA gene of SW/HN/405/10 probably was originated from avian-like H1N1 SIV and the genetic characteristics of the isolated strain showed to be comparatively stable, but some mutations appeared in the genomes which suggested that the isolated strain would continually evolve with variation in future.