Purple sweet potato is rich in protein, 18 kinds of amino acids easily digested and absorbed by the human body, vitamins, selenium, zinc, iron, copper, manganese, calcium, phosphorus, iron and more than ten kinds of natural mineral elements. It is rich in iron, calcium and selenium. And selenium and iron is the body of the essential elements for anti-fatigue, anti-aging, blood tonic, especially selenium is known as “anticancer king”, have good health care function, easy to be absorbed by human body, can stay in serum, repair the myocardium, enhance immunity, remove free radicals in the body to produce cancer, inhibit cancer cell DNA synthesis and cancer cell division and growth, Prevent the occurrence of cancer such as gastric cancer and liver cancer. A large amount of anthocyanins can be extracted from purple sweet potato, which has the strongest scavenging ability of tert-butyl peroxide free radical, and this ability increases with the increase of total phenolic content in purple sweet potato. At the same time, the anthocyanins of purple potato can prevent the lipid peroxidation caused by linoleic acid oxidation most effectively. It can also inhibit the mutation caused by heterocyclic amines. Two anthocyanins isolated from purple sweet potato have strong anti-mutation effect. Purple anthocyanins can also inhibit acute liver injury induced by carbon tetrachloride.