Abstract: Melatonin，a broad-spectrum antioxidant, can get through the biological membranes directly and reduce the intracellular oxidative stress induced by reactive oxygen species，which plays an important role in regulating cell biological activities via its special receptors. It was suggested that melatonin improved oocyte maturation and embryo development by its effect of antioxidant. The antioxidant effect of melatonin has recently been focused on. However，it is still not clear whether melatonin improves oocyte maturation and developmental potentiality of oocyte when of added into IVM culture medium. Effects of melatonin in oocyte development and in vitro maturation，as well as its potential application，was discussed in this review.

Key words: Cells, cultured, Reproductive techniques, assisted, Reactive oxygen species, Melatonin, Immaturate oocyte, in vitro maturation