Abstract: Melatonin is a natural compound, specifically an indoleamine, produced by and found in different organisms including bacteria, fungi, plants and animals, and is involved in such biological processes such as anti-oxidation, sleep-wake timing and immunity regulation.Biosynthesis of melatonin is circadian in mammals and is regulated by light and putatively by temperature. In this paper, the research progress in melatonin biosynthesis and physiological functions was summarized, the regulatory factor of melatonin biosynthesis was clarified, and the ways of high-melatonin-based functional milk preparation in different countries were introduced, respectively, so as to provide references for the application of melatonin in animal husbandry production and the preparation of melatonin-based functional milk.