Abstract: Mx protein, a GTP-enzyme active protein induced by interferon, exhibits broad-spectrum antiviral activity. As member of economically fresh water fish with superior quality, Squaliobarbus curriculus has the highest fitness and disease resistance; however, studies on its immunity are limited. In the current study, we amplified a full-length cDNA of Mx (ScMx) from the spleen by using degenerate PCR and SMART RACE, and conducted homology analysis and tissue expression analysis of ScMx mRNA in different tissues including liver, spleen, intestine, gill, kidney, head kidney, heart, brain and muscle. Furthermore, we investigated the temporal expression levels of ScMx in the liver and spleen after GCRV-104 infection. The results indicated that the full-length of ScMx gene was 2325 bp consisted of 40 bp 5'-UTR, 371 bp 3'-UTR and 1884 bp ORF encoding 627 amino acids. The theoretical molecular weight and isoelectric point (PI) of ScMx were 70.9 kD and 8.25, respectively. ScMx shared the most homology with Carassius aruatus Mx3. ScMx was broadly expressed in all tested tissues. After infected with GCRV-104, the ScMx expression levels in the liver and spleen showed a tendency of fluctuation: the relative expression of ScMx increased reached the peak at 48h after the viral infection, and then decreased. The infection significantly induced the expression of ScMx (P 0.05). These results suggested that ScMx may play an important role in the immune response of Squaliobarbus curriculus against GCRV-104 infection.