The invention discloses a use of a hybridoma cell line secreting a monoclonal antibody against rice gall dwarf viruses and a use thereof. A BALB/c mouse is immunized by a prokaryotically expressed rice gall dwarf virus (RGDV) CP recombinant protein as an antigen, and a hybridoma cell line 11B6 capable of stable passage and secretion of an anti-RGDV monoclonal antibody is obtained by cell fusion, screening and cloning and has a preservation number of CGMCC No. 14897. The indirect ELISA titer of the ascites monoclonal antibody secreted by the hybridoma cell line is 10<-8>. The antibody type andsubclass are IgG1 and kappa chains. The monoclonal antibody can react specifically with the RGDV coat protein. The ACP-ELISA and dot-ELISA methods for detecting RGDV are established through a 11B6 monoclonal antibody as the core. The sensitivity of the two methods for detecting diseased leaves is 1:327 680-fold dilution (w/v, g/mL) and 1:20 480-fold dilution (w/v, g/mL). The acquisition of the hybridoma cell line and its monoclonal antibody and the establishment of serological detection methods provide material and technical support for the detection, diagnosis and scientific prevention and control of the viral disease.