Carotenoids are widely synthesized in all photosynthetic organisms and some nonphotosynthetic prokaryotes，fungi and a few animals.In photosynthetic organisms，carotenoids，like chlorophyll，are essential pigments for photosynthesis and photoprotection.In nonphotosynthetic organs，they act as photoprotectants，antioxidants，color attractants and the precursors of plant hormone synthesis，which is conducive to the normal life activities of photosynthetic organisms.For most animals and humans，carotenoids are transferred，accumulated and metabolized by the food chain，presenting complex and diverse structures.They have the properties of scavenging free radicals，antioxidants，generating vitamin A，regulating cell signaling pathways to upregulate antioxidant enzymes and so on，so as to prevent diseases and promote the health of the body.Carotenoids’color is used for some animal sexual attraction,camouflage，photoprotector，identification of species and social relations.