To construct a prokaryotic expression system of Liza haematocheila interleukin (IL)-22,the partial IL-22 gene was cloned from spleen using the specific primers by PCR and inserted into pUC57 vector.Then,the plasmid and pQE-30 vector were digested with BamHⅠ and KpnⅠ,ligated and sub-cloned into M15.The IL-22 protein was expressed by IPTG induction,purified by Ni-NTA and confirmed by SDS-PAGE.The SDS-PAGE result showed that after induced by IPTG,the IL-22 was expressed successfully in M15,and mainly expressed in supernatant.The results indicated that the IL-22 prokaryotic expression vector was constructed successfully and the recombinant protein possessed biological activity.