The mature peptide domain of insulin-like growth factor-I from Platichthys stellatus were amplified with specific primers based on its cDNA sequence. Then the matured peptide fragment was subcloned into the prokaryotic expression vector pET-28a to successfully construct IGF-I/pET-28a recombinant plasmid which were highly expressed in E.coli BL21（DE3） after being induced by IPTG with special fusion polypeptides containing His6 at their N-terminus. The obtained IGF-I polypeptide expressed in form of inclusion bodies with molecular weight of 12.1 kD and maximally accounted for 39.8 % of the whole bacterial protein post 3 h induction with 0.5 mmol/L IPTG at 37 ℃. Western blotting analysis indicated fusion polypeptides had the antigenicity to His6 antibody. The inclusion bodies were denaturalized using 6 mol/L guanidine HCl， purified using Ni-NTA affinity chromatography and annealed by gradient dialysis in urea， then purified proteins with molecular weight of 12.1 kD which was obtained from IGF-I recombinant bacterium. The proliferation experiment showed recombinant IGF-I protein could significantly promote the proliferation of human embryonic kidney cells HEK293T at 0.6 μg/mL and inhibit the proliferation with 1.8 μg/mL which verified its biological activity. Therefore， the IGF-I prokaryotic expression system was successfully constructed in the present study and biologically active IGF-I fusion protein was obtained. The present results would be helpful for better understanding the roles of IGF-I in growth regulation and development of high effective additive for growth promotion of Platichthys stellatus.