Unc45 myosin chaperone b(unc45b)gene is a molecular chaperone that mediates the folding, assembly and accumulation of thick-filament myosin in the formation of sarcomere, which plays an important role in the development of striated muscle and the stability of sarcomere. In this study, the complete cDNA sequence of unc45b gene of grass carp was obtained by rapid amplification of cDNA ends (RACE), and the characteristics of the unc45b protein predicted from gene sequence was analyzed by bioinformatics methods. The differential expression pattern in tissues was also detected by quantitative real-time PCR. The results showed that the full-length of unc45b gene of grass carp is 3163 bp, which contains a 60 bp 5'UTR, a 298 bp 3'UTR, and a 2865 bp open reading frame (ORF) encoding a 934 amino acid peptide. The deduced unc45b protein exhibits a homology of 92, 86, 86 % with the protein of zebrafish (Danio rerio), channel catfish (Ietalurus punctatus) and tilapia (Oreochromis niloticus) respectively, and the protein contains UCS myosin head binding domain and TPR peptide repeat domain. The protein is a hydrophilic and non-secretory protein with a molecular mass and isoeletronic point of 103,699.8 and 7.39 Da. The structural elements of the protein includes α-helixes and loops, and the unc45b gene highly expresses in skeletal muscle and heart in grass carp. This study laid a foundation for further research in explaining the myofibril accumulation in crisped grass carp.