In this paper, through the collection and collation of ancient herbs, medical books and prescriptions, combined with modern literature, the historical changes of the name, origin, position, medicinal parts, collection, processing and processing of bluegrass were systematically combed and verified.It can be seen from the research that bluegrass was first used as medicine by the fruit, namely blueberry, which was originally Polygonum tinctorium. Since the Ming and Qing Dynasties, blueberry was rarely used, and it has been no longer used medicinally. In the Wei and Jin Dynasties, the medicinal parts extended to the stems and leaves, and most of them used juice as medicine.Since the Tang Dynasty, origin has been extended to Isatis indigotica, Baphicacanthus cusia, Indigofera tinctoria, Compositae plant Wulan, etc. In the Song Dynasty, the medicinal parts extended to the roots, and the "Banlangen" began to appear, and gradually became the main medicinal parts of blue medicinal materials, the main base of which was B. cusia. Since the Qing Dynasty, I. indigotica, a Cruciferae, has gradually become a genuine indigo root, while B. cusia has become a southern indigo root. It was the first mineral dye imported from abroad for thrush, and then used as medicine, also known as clam powder. Because it was found that it had the same effect with the extract of bluegrass, it was also named indigo naturalis in China, which has lasted till now. The main stream of Isatidis Folium in the past dynasties is the dry stem and leaf of Clerodendrum cyrtophylum. Since the Qing Dynasty, the stem and leaf of Isatis indigotica, P. tinctorium and other blue grasses have been gradually mixed as substitutes and gradually become the mainstream.
Keywords: Baphicacanthus cusia; Indigofera tinctoria; Isatis indigotica; Polygonum tinctorium; bluegrass medicine; textual research on materia medica.