Objective　To obtain genetic characterization of the HA1 of new isolates of influenza A （H1N1） virus. Methods　Virus was amplified in embryonated chicken eggs， the virion DNA was transcribed into cDNA by reverse transcriptase， cDNA amplified by PCR， the products of PCR were purified. Afterward， DNA sequence analysis was performed by the dideoxy-mediated chain termination method， using synthetic oligo nucleotide primers. Results　The HA1 domain of new isolates of influenza A （H1N1） virus showed that their HA1 genes were 981 nucleotide in length coding for a HA1 protein with 327 amino acids， deletion of a glycosylation site and an amino acid. The homology of amino acid sequences of protein molecules on HA1 domains of new influenza A virus when compared with A／Guifang／10／94（H1N1） and A／Bayern ／07／95 （H1N1） viruses，was 92.8％ and 91.3％ respectively； The homology of amino acid sequences of protein molecules on HA1 domains of A／Jingjun／11／98（H1N1） when compared with A／Jingjun／13／98（H1N1） or A／Jingjun／807／97（H1N1） viruses，was as high as 98％； The homology of amino acid sequences of protein molecules on HA1 domains of A／Guifang／10／94（H1N1） when compared with A／Bayern／07／95（H1N1） viruses was as high as 96％. Conclusions　The HA1 gene of　new H1N1 virus strains is　different from those of A／Guifang／10／94 （H1N1） and A／Bayern／07／95（H1N1）， they will probably be new mutation strains.