Abstract: Objective To analyze in fluenza A(H1N1) virus hem agglutin in(HA) antigengene mutations and molecular phylogenetic tree.Methods Pharyngeal swab samples from patients were collected by Centre for Disease Control and Prevention and sentinel hospitals distributed in Henan province.Influenza A(H1N1) virus strains were isolated from throat swab samples.Twenty of the virusiso latio nswere chosen to extractRN A.Prmiers were designed for RT PCR to amplify the genes encoding HA prote in.Gene and prote in sequence mutations were analyzed by sequencing.Results To tally 51 influenza(H 1N1) virus were isolated and 18 of 20 HA gene was amplified.The two gene fragm entswere 1024 bp and 654 bp, consistent with the expected size.Basic local a lingnment search tool(BLA ST) analysis showed that in fluenza A(H1N1) virus HA gene 433 T/C(N145 S/P) mutant distributed in many parts of China.Evolutionary tree analysis revealed that the poin tmutation may be come from pig people cross infection.Conclusion The individual amino acid of influenza A(H1N1) HA mutatied during the swine flu season in China, but did not change in an tigenicity.