The present invention relates to monoclonal antibodies which specifically bind to hepatitis E virus (HEV) open reading frame (OFR) 2 (SEQ IN NO:1), to their conserved variants or active fragments, or other monoclonal antibodies which are against OFR2 region and can cross react with the monoclonal antibodies according to the present invention, to the nucleotide sequences encoding them or the degeneration sequences. The present invention also discloses the antigenic determinants on hepatitis E virus OFR2 region. The present invention also discloses methods for screening isolated or recombination polypeptides or peptide mimics, the said polypeptides or peptide mimics have the characters corresponding to that hepatitis E virus OFR2 antigenic determinants 1) or 3) specifically bind to the present monoclonal antibodies 8C11 and 8H3. The present invention also discloses the polypeptides or peptide mimics and the nucleotide sequences encoding them or the degeneration sequences which are screened by the above methods. The present invention also discloses the uses of the polypeptides or peptide mimics for diagnosis and/or prevents of hepatitis E virus infection. In addition, the present invention discloses assay kits for diagnosis of HEV infection, and vaccines for prevent of HEV infection. The present invention further relates to the uses of monoclonal antibodies, the active fragments thereof or their conserved variants for preparing medicines for diagnosis, prevents and/or treatments of hepatitis E virus infection. The present invention relates to pharmaceutical compositions for treating HEV infection, to methods for preventing and/or treating HEV infection. The present invention also relates to recombination express vectors containing the said nucleotide sequences, to the recombination hosts transformed by the recombination express vectors, the recombination hosts can express the present monoclonal antibodies, their conserved variants or the active fragments thereof, the p
