||Hepatocellular carcinoma (HCC) is a common cancer affecting majority of the Chinese. Due to the problem of non-specificity, common methods of cancer treatment including systemic chemotherapy, affects not only cancer cells but also normal tissues. In order to develop a specific treatment for HCC, a murine anti-human HCC monoclonal antibody was raised in 1991. However, murine monoclonal antibodies will cause HAMA (Human Anti-Murine Antibody) reaction when injected into human body, hence they are not ideal for use in human cancer therapy. One way to prevent the HAMA reaction is to "umanize" the murine monoclonal antibody before clinical application. The aim of humanization is to reduce the murine monoclonal antibody's immunogenicity while maintaining its binding activity. Human consensus sequence was used as a template to design the amino acid sequence of the humanized antibody variable region, and synthetic DNA molecules for protein expression were produced through overlapping PCR from single strand oligonucleotides. The synthetic DNA molecules and human antibody constant region cDNA were used to construct two human cytomegalovirus promotor-based expression vectors for both antibody light chain and heavy chain. Completely assembled humanized antibody was expressed in mammalian cells and purified using protein A. The humanized antibody has been found to have binding activity to a human liver cancer cell-line (SMMC-7721).