Total RNA was isolated from grass carp ( Ctenopharyngodon idellus ) liver tissue. The cDNA encoding insulin-like growth factor I ( IGF-I) peptide was amplified by reverse transcript ion polymerase chain reaction ( RTPCR) strategy using isolated total RNA as template. The amplif ied cDNA fragment was inserted to vector pUC18. The cloned cDNA was sequenced and the amino acid sequence of grass carp IGF-I was predicted. The nucleotide sequencing showed the cDNA encoded 117 amino acids including B, C, A, D and E f ive domains. The nucleotide sequence and deduced amino acid sequence shared 93. 8% and 97. 1% homology with that of common carp mature IGF-I. Analysis of E domain indicated that cloned grass carp IGF-I belonged to IGF-IEa-2 subtype.