The recombinant protein of cathepsin B in Marsupenaeus japonicus was obtained by prokaryotic expression.Opening reading frame of the cathepsin B gene was amplified with specific primer which containEco RⅠand NotⅠrestriction sites and 6×His tag from the ovary,connected with expression vector pGEX 4T2 and introduced into E. col BL21.The optimal induction was acquired at 5 h with IPTG concentration of 1 mmol/L at 30 ℃.The recombinant protein was purified by His affinity column.A series of urea buffers (8 mol/L,6 mol/L,4 mol/L,2 mol/L,1 mol/L and 0 mol/L) were used for gradient dialysis.The soluble recombinant proteins were preserved in -80 ℃ after freezedrying.The molecular weight of the protein was 63 ku measured by SDS-PAGE.The polyclonal antibody was prepared by using the freezedried proteins,and the antiserum titer of antibody was 50 000 by ELISA. The specificity of it can be detected by Western blot.The preparation of antibody laid the foundation for protein expression and gene function study of cathepsin B.