Hepatitis C virus (HCV) antibody diagnostic kit (enzyme-linked immunosorbent assay, ELISA) is developed by Runkun Pharmaceutical Co. Ltd. in cooperation with the Institute of Basic Medical Sciences under the Academy of Military Medical Sciences of the Chinese People's Liberation Army, and used to screen blood for HCV antibody and to help with the diagnosis of clinical patients. It is now China's only diagnostic kit of double-antigen sandwich ELISA for HCV antibody approved by the State Food and Drug Administration (SFDA). It is also known as the diagnostic kit of "the fourth generation" for HCV antibody. The use of the advanced "double-antigen sandwich ELISA" has significantly improved t he specificity and sensitivity of the diagnostic reagent, adding a firewall to blood transfusion safety in our country. The testing reagent of double-antigen sandwich ELISA for HCV antibody is prepared with agents such as microporous enzyme-linked plate coated with multi-epitope chimeric antigen of HCV (RHCV-NS4-C-NS3-NS5), biotin-LC marked by modified chimeric antigen of HCV (LC-Biotin-HCV-Ag), horseradish peroxidase marked by chain enzyme avidin (SA-HRP)and other supportive reagents, to detect the HCV antibody in sera by employing the double-antigen sandwich ELISA (Sandwich-ELISA).