miR-29a/b1 was reported to be involved in the regulation of reproductive function in female mice, but the underlying molecular mechanisms were not clear. In this study, female mice lacking miR-29a/b1 showed a delay in vaginal opening, irregular estrus cycles, ovulation disorder and infertility. However, the development of egg was normal in mutant mice and the ovulation disorder could be rescued by the superovulation treatment. The plasma level of luteinizing hormone (LH) was significantly lower in the mutant mice. Using iTRAQ coupled with LC-MS/MS, we found that the deficiency of miR-29a/b1 in mice resulted in an abnormal expression of a number of proteins involved in vesicular transport and secretion in the pituitary gland. The miR-29a/b1 targeting gene Dnmt3a and Hdac4 were up-regulated in the pituitary of miR-29a/b1 knockout mice suggesting that these two epigenetic writers may be the upstream causes for these phenotype changes due to miR-29a/b1 deficiency. These findings demonstrated that miR-29a/b1 is indispensable for the function of the reproductive axis through regulating LH secretion in the pituitary gland.