The examples of compatibility use of incompatible medicaments are abound. Does the practice of complying with eighteen incompatible medicaments affect the curative effect? Whether will the incompatible medicaments necessarily cause toxic reactions even death? They are issues open to discussion. The compatibility of incompatible medicaments is usually considered in specified pathological conditions clinically. This paper suggests that we can study the classical Prescriptions that include incompatible medicaments, to sum up various kinds of compatibility conditions in the specified pathological conditions based on the clinical applications. These studies are of theoretical and practical significance to guide reasonable applications of incompatible medicaments and to perfect the compatible theory of TCM.