The invention relates to a specific binding protein and an application thereof and particularly provides a monoclonal antibody which can be effectively bound with an epidermal growth factor receptor mutant III (EGFRv III) or partially bound with an epidermal growth factor receptor (EGFR) with overexpressed cells, but has no binding effect with an EGFR with normally expressed cells. In addition, the monoclonal antibody has obvious therapeutic effect on a tumor cell line which expresses the EGFRv III. The invention also provides a method for preparing the monoclonal antibody and a medical composition containing the monoclonal antibody.