To study the relationship between the concentrations of INH B (Inhibin B), ACT A (Activin A), and FSH (Follicle stimulating hormone) in blood plasma and fecundity, Dazu black goat with high productivity and Sannen dairy goat with low productivity were used as experiment objects in this research. The concentrations of INH B, ACT A, and FSH in blood plasma were measured by enzyme-linked immunosorbent assay (ELISA) in order to study the secretion rule of INH B, ACT A, and FSH during an estrus cycle of two goat breeds. The results indicated that the secretion of FSH showed a positive correlation with ACT A and a negative correlation with INH B. The mean concentration of FSH in Dazu black goat was higher than that in Sanen dairy goat during a estrous cycle. However, during the time from obviously estrus to ovulation, the mean concentration of FSH in Dazu black goat was significantly higher than that in Sannen dairy goat (0.01<P<0.05). These results showed that during an estrus cycle, the differences in INH B, ACT A, and FSH might be the reason for fecundity differences. Activin A might not be responsible for the number of eggs ovulated of goats. The main effect of ACT A may be extention of follicular stage. Inhibin B indirectly influences ovulation by regulation of FSH level.