Employing PCR method , the cloned grass carp IGF2 Ⅰgene was modified to be a mature IGF2I peptide gene and then subcloned into fusion expression vector pGEX24T21 to construct expression vector pGEX2IGF. Restriction endonuclease analysis and sequencing confirmed the corrected construction. The vector was transformed into Escherichia coli BL21 cell which can be induced by IPTG to produce a special protein of 34kD in molecular weight. The special protein can be mainly in form of soluble protein or inclusion body when induced at 30 and 37 ℃ respectively. The cells induced at 30 ℃ were digested by lysozmye and disrupted by sonication. After being centrifuged the supernatant was purified by glutathione sepharose column. GST2IGF fusion protein could be absorbed specifically on this column. The high purified protein was used as antigen to immune rabbits directly and high quality antiserum was obtained , which showed that the fusion protein possesses good immunogenicity.