Black tea is a kind of tea processed by withering, rolling, fermentation, drying and other processes. Especially through the fermentation process, a series of biochemical changes have taken place in the content of tea, which constitutes the quality characteristics of black tea and black tea soup. As the green leaves turn into red leaves after fermentation, it is called black tea, also known as fermented tea. The quality style of black tea is quite different from that of green tea. Green tea is valued for keeping its natural green color, while black tea is valued for its red color. Black tea is a kind of tea with the largest output, the widest market and the largest sales volume in the world. According to different production methods and product quality, China's black tea is divided into Kungfu black tea, small black tea and broken black tea.