The engineered NS0 myeloma cell line was used to express recombinant anti-human CD25 chimeric monoclonal antibody.The cell cultivation and expression process was investigated in a 5 L cell reactor.The average yield of target product in cell suspensions was 108 mg/L, and about 4 L cell suspensions were harvested from each batch.The target product with purity over 95% and recovery rate around 33% was purified from harvested supernatant by a two-step purification process using rProtein A Sepharose FF and SP Sepharose FF chromatog.Western blotting proved that the expressed and purified protein was identical to the target product and retained the immunogenicity of the target product.Anal. result showed that fifteen amino acid residues of the N-terminal were identical to the theor. sequence.