Abstract: Objective To better elucidate the prevalence and analyze evolution characteristics of neuraminidase (NA) gene of influenza A (H1N1)pdm09 virus circulating in Yantai from August 2009 to August 2017. Methods A total of 10 236 swabs were collected among patients with an influenza-like illness (ILI) admitted to 2 sentinel surveillance hospitals of Yantai from August 2009 to August 2017. All specimen were cultured in Madin-Darby canine kidney (MDCK) cells and identified by hemagglutination inhibition assay. Complete sequences of NA of 43 influenza A (H1N1)pdm09 strains circulating in Yantai were amplified, sequenced and analyzed using molecular and phylogenetic methods. Results The phylogenetic analysis showed that most strains grouped into genetic clades 2,7, 6C, 6B.1 and 6B.2. Compared to the vaccine strain, the amino acid substitution N44S occurred in clades 6 and 7 strains, resulting in an increase in the number of glycosylation sites. The N386K substitution appeared in subclades 6B.1 and 6B.2 strains, contributing to a loss of glycosylation site. Two positive pressure sites (34 and 386)were observed in NA proteins by FEL and IFEL model.The catalytic sites of the NA protein were conserved among all the influenza A (H1N1)pdm09 strains isolated in Yantai area. Conclusions All the influenza A (H1N1)pdm09 virus circulated in Yantai from August 2009 to August 2017 presented continual genetic variation and were still susceptible to neuraminidase inhibitors. Continuous epidemiological and virological surveillance are necessary.