PURPOSE: To explore the effects of prepubertal obesity induced by high-fat diet during lactation and post-weaning on puberty onset and the neuroendocrine changes before puberty onset in a female mouse model, which may explain obesity in children starting early puberty. METHODS: A total of 72 female mice were assigned to the high fat diet group (HFD) and the control diet group (CONT) during lactation and post-weaning. The bodily indexes; pathological changes; and protein and gene expression levels in the hypothalamus were examined on postnatal days (P) 15, 28, and 45, respectively. RESULTS: The average vaginal opening time in HFD mice occurred significantly earlier than that in CONT mice (p < 0.05). On P15, no significant difference in the MKRN3, kisspeptin, GPR54 and GnRH level between HFD and CONT mice was noted (p > 0.05). Whereas on P28 and 45, compared to CONT mice, GnRH expression in HFD mice was significantly increased (p < 0.05); kisspeptin and GPR54 expression in HFD mice was also significantly increased (p < 0.05); but the MKRN3 level in HFD mice was significantly lower than that in CONT mice (p < 0.05). On P15, 28, and 45, compared with CONT mice, miR-30b expression in HFD mice increased (p < 0.05). Compared to P15, miR-30b, KiSS-1, GPR54 and GnRH mRNA level increased significantly, however MKRN3 decreased significantly in HFD mice on P28 and 45 (p < 0.01). CONCLUSIONS: Prepubertal obesity induced by high-fat diet during lactation and post-weaning may advance the time of pubertal initiation in female mice. The increased expression of miR-30b, kisspeptin, GPR54 and GnRH, decreased the expression of MKRN3 may explain the early onset of puberty in obese female mice.