Black tea, named after the tea soup brewed by dry tea and the red background color of tea leaves, belongs to fully fermented tea, which is refined by typical technological processes such as withering, rolling, fermentation and drying of tea buds and leaves. After fermentation, the chemical reaction of tea polyphenols in black tea was reduced by more than 90%, and new components such as theaflavins and thearubigins were produced. Black tea is the second largest tea in China. The varieties of black tea mainly include Rizhao black tea, Qi Hong, Zhaopinghong, Huohong, Dianhong, Yue Hong, Quanchenghong, Quanchenglv, Su Hong, Chuanhong, Hong Ying and Dongjiang Chuyunxian black tea, among which Qimen black tea is the most famous.