By investigating the mainstream works of herbal classics of successive ages, it is found that adulteration of Chinese materia medica appeared early in ancient China. The main methods of adulteration was producing fraud medicines in the Northern-Southern Dynasties, fake medicines began to appear in the Tang Dynasty, and status of adulteration of Chinese materia medica ran unchecked since the Ming and Qing Dynasty. By statistics, there were 76 kinds of adulteration varieties before the Republican period. The main varieties were precious drugs, animal drugs and artifacts. Commonly methods used in the process included forging and adulterating, dealing with 11 kinds and 68 kinds respectively. Adulteration probably lead to the result of imposing the changes of the used medicinal parts of Herba Pogostemonis; Radix Aconiti Lateralis prepared by adding salt, Radix Angelica Sinensis processed by wine, and Radix Astragalis seu Hedysaris processed with bee honey. However, the root cause of adulteration in Chinese materia medica was the dissociation of professional physician and pharmacist, resulting in the ignorance of medical practitioners became unable to recognize Chinese materia medica; and the immorality of medicinal merchants. Besides, rating the quality of materia medica based on its producing areas without differentiating the false from the genuine may also contribute to this result passively.