For the first time, a comparison of the catechins content in green tea samples of the main producers of this drink: China, India, Sri Lanka, Vietnam, Indonesia. Catechins are the main polyphenols-antioxidants of green tea. They provide its high antioxidant activity and a positive effect on human health. The main catechins in green tea are from six to twelve, they are usually determined by HPLC with different detection systems. The consumption of green tea with a high content of catechins reduces the risk of dangerous diseases: cardiovascular, oncological, neurodegenerative and others. Catechins suppress a dangerous bacterium, Helicobacter pylori, which causes stomach diseases, and beneficially affect the microbiota of the human intestines. The most active catechinepigallocatechin gallate inhibits even the metastases of certain cancers. Green tea catechins reduce the activity of influenza virus and other viral diseases.