Abstract: The current study reported the identification and characterization of arginine kinase (AK) of shrimp Macrobrechium rosenbergii (denoted as MrAK). The full length cDNA (1740 bp) of MrAK was identified by SSH cDNA library construction and RACE approaches. Its open reading frame (ORF) was 1068 bp encoding a polypeptide of 355 amino acids. The deduced amino acid of MrAK had a potential ATP:guanidine phosphotransferases active site:(Cys286-Pro287-Thr288-Asn289-Leu290-Gly291-Thr292). Homology analysis showed that the putative MrAK shared 97%, 82%, 83% and 79% identities with AKs from Neocaridina denticulata, Euphausia superba, Lepeophtheirus salmonis, and Pseudodiaptomus annandalei, respectively. The phylogenetic tree analysis indicated that MrAK was similar to invertebrate AK, suggesting it has high evolutional conservation. Moreover, the expression of MrAK significantly up-regulated at 9h post-MrDV (M. rosenbergii dicistrovirus) immune challenge and reached peak level at 12h post-challenge. These findings suggest that MrAK might involve in host defense system against MrDV infection.