Green tea is one of the six major teas in China, which belongs to non-fermented tea. It refers to the beverage made by deactivating enzymes, rolling and drying after picking new leaves or buds of tea leaves without fermentation. The color of the finished tea is the same as that of the brewed tea soup and leaf bottom, and it is mainly green, so it is named green tea. Polyphenols such as catechins in green tea are recognized as key components beneficial to health in green tea, which have many health-care functions, including preventing cancer, improving cardiovascular health, losing weight, and resisting radiation.