Abstract: The effect of gap junction on bovine oocyte maturation and cumulus expansion in vitro was studied by means of treating bovine oocyte with different density of FSH. The results indicated that the optimal density of Follicle-Stimulating Hormone （FSH） was 1.2 IU/mL and the gap junction between oocyte and cumulus cell in vitro had direct influence on bovine oocyte maturation. Furthermore, the gap junction can stimulate bovine oocyte maturation and cumulus expansion in vitro.