Traditional chemotherapy has become one of the essential treatments of cancer.  However,   cytotoxic agents are not tumor specific, which would cause serious side effects.  Antibody-drug conjugates (ADCs), also called immunoconjugates, belong to the “targeted chemotherapeutics” category of anti-cancer drugs.  ADCs are composed of three components including the cytotoxic drug, the monoclonal antibody, and the linker connecting the drug to the antibody.  With the special-binding between antibody and antigen expressed on the surface of targeted cancer cells, ADCs provide a method to achieve excellent localization of the drug at the   desired site in the body.  The internalization and formation of ADCs are crucial in designing and applying an antibody conjugate to a particular disease model.  In this review, we summarize three distinct internalization routes of ADCs and analysis the structure of ADCs.  We also discuss in detail the categories and interaction of every component, as well as their influence to targeting property, liability and activity.