Abstract: Companion diagnostics (CDx) and CDx related antitumor drugs develope very fast recently for the improvement of basic research of oncomolecular biology. Antitumor drugs is the largest branch of CDx nowadays. Doctors may prognosis drug effect by CDx, which is important in making treatment plan and individualized treatment. There are many differences between traditional chemotherapy drugs and CDx related drugs. Here is a review of companion diagnostics related antitumor drugs.