Abstract: Insulin-like growth factor-Ⅰ(IGF-Ⅰ) is a single-chain polypeptide with structural homolog to proinsulin.It plays an important role in regulating somatic growth in vertebrates via growth hormone.To study fish IGF-Ⅰs structure,function and its potential application in aquaculture,we cloned the insulinlike growth factor-Ⅰ cDNA from bluntnose bream (Megalobrama amblycephala).Total RNA was isolated from liver tissue.The cDNA encoding IGF-Ⅰ peptide was amplified by reverse transcription polymerase chain reaction (RT-PCR) strategy using isolated total RNA as template.The amplified cDNA fragment was inserted to vector pUC18.The cloned cDNA was sequenced and the amino acid sequence of bluntnose bream IGF-Ⅰ was predicted.The nucleotide sequence showed that the cDNA encode 161 amino acids including signal peptide and B,C,A,D,E six domains.Analysis of E domain indicates that the cloned bluntnose bream IGF-Ⅰ cDNA belongs to IGF-ⅠEa-2 subtype.