The cytoplasmic domain of human erythrocyte band 3 (cdb3) plays an important role in connection of the membrane with the membrane skeleton, and environment inside the cell as well. With whole length of band 3 gene, cdb3 gene was amplified by PCR and then was cloned into pRSET plasmid. The plasmid was introduced into E.coli BL21(DE3). The cdb3 expression proteins were purified and its function was verified according to the ability to inhibit aldolase.