This invention provides a B cell epitope peptide and its identification method to neutralize helicobacterpylori urease B subunit, determines the antigen epitope corresponding with the monoclonal antibody 6E6 of helicobacterpylori urease B subunit, and confirms this B cell epitope is specific for the 6E6. The invention also provides a chimeric epitope vaccine and its preparation method containing B cell epitope and carrier protein BSA, and the B cell epitope has strong antigenicity.