Chinese herbal medicine is a vital part of traditional Chinese medicine (TCM). As we all know, some Chinese herbal medicines have toxic side effects, while applications of the drugs by compatibility under the guidance of the theoretical system of TCM can reduce the toxic side effects and even exert synergistic effects. This article described the basic principles of the attenuation and synergy of drugs by compatibility from the perspective of drugs compatibility in the TCM "classical and current prescriptions" , and listed the examples of clinical applications of TCM drugs by compatibility, in order to clarify the mystery of the attenuation and synergy of TCM drugs by compatibility.