Abstract: IGF cDNA of Protonibea diacanthus was obtained by using the method of RACE and RT-PCR for the first time in this study. The full length sequence is 842 bp, which contains 648 bp open reading frame (ORF), 125 bp 5untranslated region (UTR), and 69 bp 3' untranslated region. IGF2 precursor mRNA encodes 215 amino acids, while the mature polypeptides contains 71 amino acid residues. IGF2 of Protonibea diacanthus has a high homology with that of other fishes. It has 95.8%, 95.3%, 91.2% homology with Epinephelus coioides, Sparus aurata, Oreochromis niloticus, respectively. Phylogenetic tree analysis shows that the IGF2 of Protonibea diacanthus tends to cluster with E. coioides, S. aurata, O. niloticus of the same genus firstly, then clusteres with IGF2 of Oncorhynchus mykiss, Ietalurus Punetaus, Pelteobagrus fulvidraco and IGF2b of Danio rerio in turn. Finally IGF2a of Danio rerio is clustered in the same branch with bony fishesIGF2. Tissue distribution shows that IGF2 is widely expressed in multiple tissues of P. diacanthus. RT-PCR reveales that the highest expression of IGF2 of ovary is detected in maturation phase and regression phase than that development phase. IGF2 expression may relate with ovarian maturation of P. diacanthus.