According to the color of sweet potato pulp, there are red sweet potatoes, white sweet potatoes and purple sweet potatoes. Sweet potato belongs to the family Convolvulaceae of the genus Panicum, which is more than 2 meters long and lies on the ground. Its leaves are usually wide oval, 4- 13 cm long and 3- 13 cm wide. Corolla pink, white, lavender or purple, bell-shaped or funnel-shaped, 3-4 cm long, and capsule ovoid or oblate. Sweet potato is rich in protein, starch, pectin, cellulose, amino acids, vitamins and various minerals, and has the reputation of "longevity food". The sugar content reached 15%-20%. Has anticancer, heart protecting, emphysema and diabetes preventing, and weight reducing effects. Li Shizhen's Compendium of Materia Medica in Ming Dynasty recorded that "sweet potato can tonify deficiency, strengthen spleen and stimulate appetite, and strengthen kidney yin", and said that people in the sea can eat for a long time. Chinese medicine regards sweet potato as a good medicine.