The recombinant plasmid containing a synthetic grass carp growth hormone cDNA was transformed into Escherichia coli BL21 (DE3) and expressed efficiently, induced by 1 mmol/L IPTG. 12.5% SDS-PAGE showed the molecular weight of new added protein in Escherichia coli BL21 (DE3) is consistent with that of grass carp growth hormone. The recombinant protein was composed of approximately 40% of the total bacterial proteins. The target protein was purified with Ni-NTA affinity column. Western-blotting conformed that recombinant protein could specifically react with antibody against grass carp growth hormone. ELISA-receptor assay showed the bioactivity of recombinant protein is consistent with that of nature grass carp growth hormone.