Abstract: Melatonin as a unique antioxidant, and its receptors, exist in multiple tissues or cells. Melatonin exerts a series of biological effects not only through the activation of melatonin receptors including high-affinity transmembrane receptor and nuclear receptor, but also through the unique antioxidant protection by directly removing reactive oxygen species (ROS) or by activating antioxidative enzymes. One of the key factors of assisted reproductive technology (ART) is the quality of gametes and embryos. However, the degeneration and death of oocytes and embryos are the most critical factors affecting the success rate of ART. Melatonin can not only promote the maturation of immature oocytes, improve the quality of oocytes and the development of embryos, but also protect ovarian granulosa cells and sperm after freezing and thawing. In this paper, we review the research progress of the protective effect of melatonin on oocytes, embryos, ovarian granulosa cells and sperm in ART. 

Key words: Melatonin；, Antioxidants；, Reproductive techniques, assisted；, Oocytes；, Spermatozoa；, Embryonic development；, Reactive oxygen species