Abstract: 【Objective】To prepare broad-spectrum monoclonal antibody against N protein of avian infectious bronchitis virus(IBV),so as to lay a foundation for identifying conservative domain epitope of N protein and establish a universal IBV detection method.【Method】N protein of GX-YL5,a representative strain of IBV dominant serotype in Guangxi,was expressed in prokaryote. BALB/c mice were immunized with the purified protein. After the serum titer of the immunized mice reached 10⁴ or more,the splenocytes were fused with SP2/0 myeloma cells. After screening by indirect ELISA,monoclonal antibody was prepared by ascites-induced method. Western blotting,IFA and indirect ELISA were used to identify the titer,subtype,reaction specificity and cross-reaction spectrum. And the prepared monoclonal antibody was used for immunohistochemical detection. And the prepared monoclonal antibody was used to detect the IBV in the trachea and kidney tissues of SPF chickens artificially infected with 4 representative IBV variants(GX-N130048,GX-N160421,GX-QZ171023 and GX-QZ170728).【Result】The prepared monoclonal antibody N2D5 had a titer greater than 2¹⁷ and its subtype was IgG2b. The Western blotting and IFA results showed that the monoclonal antibody N2D5 only reacted with IBV,and were negative with Newcastle disease virus(NDV),infectious laryngotracheitis virus(ILTV),avian metapneumovirus(aMPV),infectious bursal disease virus(IBDV),avian leukosis virus(ALV) and Marek's disease virus(MDV). Monoclonal antibody N2D5 reacted with many genotypes in China and all 7 serotypes of IBV currently prevalent in Guangxi,including commonly used standard strains,vaccine strains and field strains. Immunohistochemistry showed that the virus signals could be detected in the trachea and kidney tissues of SPF chickens at different time after artificial infection of 3 representative IBV strains from chicken and 1 isolated strain from duck,which further proved its broad spectrum.【Conclusion】The monoclonal antibody N2D5 of IBV prepared based on hybridoma technology belongs to the IgG2b subtype. It has the characteristics of high specificity,wide response spectrum and strong binding ability with IBV.It can be used as a specific diagnostic antibody for clinical diagnosis of IBV and the study of virus distribution.