In the present study, we identified immunodominant linear B cell epitopes on the H1N1pdm virus HA protein by a peptide scanning approach using H1N1pdm patients sera. We confirmed that an unidentified epitope was highly conserved among H1 subtypes viruses and showed a good correlation with results obtained using the HI test. These findings demonstrate the potential of epitope-based antibody detection in IAV diagnosis and surveillance.