Shennong Bencaojing was orignally recorded in Qi Lu of the Liang Dynasty and Tangye Jingfa (about prescriptions) was originally recorded in Hanshu Yiwenzhi. According to the norm of the development of knowledge, knowledge about medical herbs should have been formed before that of prescriptions. In accordance with literature, Tangye Jingifa is recorded in QI Lue of the Western Han Dynasty,which was compiled much earlier than Shennong Bencaojing. So where was the knowledge about herbs recorded in the Western Han Dynasty and before? It was found after textual research that knowledge about medical herbs was recorded together with prescriptions long before the Han Dynasty. In the Western Han Dynasty, Liu Xiang and his colleagues placed herbs under the catalogue of prescriptions when they proofread books. In the Eastern Han Dynasty, materia medica became a single category due to the need to compose prescriptions according to syndrome differentiation and the standardization of herbal administration.