The purple sweet potato, also called black potato, has purple to dark purple flesh. It is rich in selenium and anthocyanins in addition to the nutrients of ordinary sweet potatoes. Purple potato is one of the main raw materials for anthocyanins. Purple potato likes warm climate environment, stem and leaves suitable growth temperature of 18 ~ 25 ℃, temperature below 15 ℃ stop growing. The optimum growth temperature of tuber is 22～24℃, and it stops expanding when the temperature is lower than 20℃. Twining vine; tuber wild mostly cylindrical or rod-shaped, cultivated shape varies greatly, palmate, rod-shaped or conical, surface brown or black, section white, yellow or purple.