Melatonin (MT) increases oocyte maturation by reducing reactive oxygen species level and enhancing oocyte antioxidant capacity. However, the mechanisms via which MT works are still poorly understood. In the present study, the effects of MT on the maturation rate and development ability of bovine oocytes were investigated. Then, the transcriptome of oocytes treated by MT was sequenced. Finally, the expression of gap junction protein alpha 4 (GJA4) protein and cAMP level were detected in bovine oocytes, and isoprenaline (enhancer of gap junctional intercellular communication (GJIC)) and heptanol (inhibitor of GJIC) were used to investigate the effect of MT on GJIC activity in bovine oocytes. Our results showed that MT significantly improved the maturation, developmental ability and mRNA expression of GJA4 of bovine oocytes. Meanwhile, MT significantly increased GJA4 protein level and cAMP level in bovine oocytes. In contrast to heptanol, both isoproterenol and MT significantly increased GJIC activity, nuclear maturation and the development ability of bovine oocytes. However, MT significantly restored the nuclear maturation and developmental ability of oocytes treated by heptanol. In conclusion, our results showed that MT improves the maturation and developmental ability of bovine oocytes by enhancing GJIC activity via up-regulating GJA4 protein expression in IVM progress.