This invention discloses a competitive monoclonalantibody against bovine ephemeral fever virus (BOF) and its application in constructing a competitive ELISA kit, belonging to the field of monoclonalantibody technology. The technical problem this invention aims to solve is how to accurately detect BEF. This invention provides a competitive monoclonalantibody against BEF, wherein the amino acid sequence of the heavy chain variable region of the monoclonal antibody is shown in SEQ ID NO.2; and the amino acid sequence of the light chain variable region of the monoclonal antibody is shown in SEQ ID NO.7. This enables rapid and accurate diagnosis of BEF, facilitating timely implementation of prevention and control measures and reducing the risk of epidemic transmission.