Research and development of antitumor monoclonal antibody agents have shown substantial progress. Monoclonal antibodies (McAb) or their immunoconjugates can be used as therapeutic agents for cancer treatment. As reported, McAb agents display specific binding to tumor-related targets, exhibit selective cytotoxicity to target cancer cells, and show highly therapeutic effects in animal experiments. Currently, some of the McAb agents have been applied in clinical therapy. Major trends in the study of McAb agents are searching for new relevant molecular targets, humanizing of the antibody, and downsizing of the immunoconjugate molecule. Because McAb is highly specific to related molecular target, there is a great potential to develop highly effective antitumor agents. McAb agents may play an important role in cancer therapy.