This invention relates to the minimal motif of an epitope on the E6 protein from human papilloma virus (HPV), and this minimal motif of the epitope induces a monoclonal antibody having cross-reactivity with some homologous proteins of HPVs. The inventors are the first to identify a fine antigenic epitope only existing conservatively on the E6 proteins of high risk HPV16, 33, 52 or 58). Therefore, the peptides comprising this epitope can be used to prepare immunogen or serological detection antigen against the HPV E6 proteins, or to prepare specific universal antibodies for a variety of high-risk/carcinogenic HPVs.