Betalain is a kind of natural plant pigment mainly exists in Caryophyllales. It can be divided into betacyanins and betaxanthins. Betalain not only has the function of attracting insects for pollination, but also can act as an important osmoregulation substance and non-enzymatic antioxidant to help plants to defense against various biotic and abiotic stress cues and maintain normal physiological activities. Betalain has unique biosynthetic pathway and important medical and health value, and has been widely used in food, medicine and cosmetics. Combining with the latest research progress at home and abroad, this paper introduced the betalain from the aspects of physical and chemical properties, biosynthetic pathway, biological functions and application value, especially focused on the relationship between betalain and anthocyanin and the effects of light on betalain biosynthesis, so as to provide reference for further understanding and utilization of betalain.