Abstract: Gill plays an important physical barrier role in defending environmental microbes. How are im-mune responses to endogenous viruses in gill? In the present study, mRNA expressions of 12 antiviral im-mune-related genes were examined by quantitative real-time RT-PCR (qRT-PCR) in grass carp (Ctenopha-ryngodon idella) gill after grass carp reovirus (GCRV) challenge. The relative values of CiTLR3, CiTLR7, CiTLR22, CiRIG-I, CiMDA5, CiLGP2, CiNOD1, CiNOD2 and CiIFN-I were almost up-regulated at 12h, 24h, 48h and 72h. Additionally, the mRNA expression of CiIgM was triggered at 72h. However, relative expres-sions of CiMyD88 and CiIPS-1 were down-regulated at 6h, and subsequently increased. To further verify the reliability of viral infection, VP4 gene (outer capsid protein of GCRV, segment 6) was checked by RT-PCR amplification. The results indicate that gill serves as an important immune organ, and plays crucial roles in triggering antiviral immune responses in grass carp.