In the process of black tea processing, there is a chemical reaction centered on enzymatic oxidation of tea polyphenols. The chemical composition of fresh leaves changes greatly. Tea polyphenols are reduced by more than 90%, and new components such as theaflavin and thearubin are produced. The aroma substance increased significantly compared with fresh leaves. Therefore, black tea has the characteristics of black tea, red soup, black leaves and sweet taste. Black tea is a kind of fully fermented tea, which is made from the new leaves of suitable tea trees by a series of processes such as withering, rolling (cutting), fermentation and drying. Withering is an important process in the primary production of black tea. Black tea is named for the red color of the tea soup and leaves after its dry tea brewing.