Abstract: The inclusion bodies of 3A were dissolved in 8 mol/mL urea buffer, and dithiothreitol(DTT) was added as reducing agent. Result showed that after one and a half hour, the concentration of soluble protein was (26.2) mg/mL.Being separated by sephadex G75 gel filtration chromatography, the recovery and purity of protein 3A determined by SDS-PAGE were 85.82% and 100% respectively, and its molecular weight was 10 ku. By multi-step dilution, the protein 3A was refolded, and the inhibition rates measured by MTT was 93.4%.