As an essential trace element, selenium is an important component of some antioxidant enzymes (glutathione peroxidase) and selenium-p protein in human body, which plays a role in balancing redox atmosphere and improving immunity. Selenium cooperates with vitamin E in vivo to form antioxidant enzymes in vivo, which can protect cell membrane from oxidative damage and maintain its permeability. Selenium -P protein has the function of chelating heavy metals and other poisons and reducing the toxicity of poisons. Trace selenium can prevent cancer and protect the liver. Some foods contain high selenium, such as seafood, edible fungi, meat, eggs, broccoli, purple potato, garlic and other foods. Organic selenium can also be supplemented by selenium-enriched foods, such as selenium-enriched rice, selenium-enriched eggs, selenium-enriched mushrooms, selenium-enriched tea, selenium-enriched malt, selenium ester polysaccharide, selenium yeast and so on. Selenium supplementation should not be excessive, because excessive intake of selenium can lead to poisoning, hair loss, nail loss and so on. Selenium supplements should be taken strictly and accurately, and it is recommended to take selenium supplements certified by the state. The selenium content in the diet in most areas of China is sufficient and safe.