The invention provides an immunogenic peptide of hKv1.5 and a purpose thereof. The peptide comprises continuous thirteen amino acids on an extracellular ring between an alpha-subunit transmembrane segment S5 and an alpha-subunit transmembrane segment S6 of the hKv1.5, and the amino acid sequence of the peptide is Glu-Ala-Asp-Asn-Gln-Gly-Thr-His-Phe-Ser-Ser-Ile-Pro. An antibody which aims at the peptide and is prepared with an immunological method can be used as a new specific inhibitor of the hKv1.5 and a super-rapidly activated delayed rectifier potassium channel coded by gene of the hKv1.5, and can be used to research the adjustment of functions of the hKv1.5 and the super-rapidly activated delayed rectifier potassium channel coded by the gene of the hKv1.5. The preparative monoclonal antibody and a vaccine based on the peptide are helpful for the atrial fibrillation treatment.