Abstract: In this study, we investigated the effects and mechanisms of estrus rate, estrus and gonadal axis on female rabbits. A total of 48 5-month-old female New Zealand rabbits, not multiparous, were reared in artificial illumination. They were randomly assigned to 3 groups of 16 each. All groups were reared in 12-h L/12-h D photoperiod for the first 10 days, then the 3 groups were reared in long light group (LD, L:D 16:8), control group (L:D 12:12) or short light group (SD, L:D 8:16) for the last 6 days separately. Light intensity is 80 lx. The blood, hypethalamus, pituitary and ovary were collected, and estrus ratio was recorded. Effects of photoperiod on secretion of development of follicular and gonadotropic hormone were investigated by HE staining, ELISA, real-time PCR methods. Our results revealed that the serum melatonin level in LD was significantly decreased by 34.8%, 47.8% compared to control and SD groups (P<0.05). Meanwhile,the serum melatonin level in SD was 25% higher than that of control group (P<0.05). The GnRH mRNA expression of the hypothalamus in the rabbit exposed to LD was increased. The GnRH mRNA level of hypothalamic significantly increased by 453%, 250% compared to SD and control groups (P<0.05), while there was no significant difference between SD group and control group (P>0.05). Similarly, the GnRH mRNA level of the pituitary exposed to LD significantly was increased by 70%, 41.7% compared to SD group and control group (P<0.05), while there was no significant difference between SD group and control group (P>0.05). The level of serum follicle stimulating hormone(FSH) in the LD group was 33.7% and 25.1% higher than those of SD group and control group significantly (P<0.05, respectively). Serum luteinizing hormone(LH) level in the LD group was significantly increased by 54.2% as compared to SD group (P<0.05). The level of serum estradiol in the LD group was significantly increased by 34.8%, 47.8% compared to control group and SD group (P<0.05). The number of primary follicles per unit area in long photoperiod group was 120% and 68.3% higher than those of short photoperiod group and the control group (P<0.05). There were no significant differences in the number of antral follicles per unit area of the ovary among groups (P>0.05). Compared to control group (31.25%), estrus ratio of long photoperiod group increased to 81.25%, while that of short photoperiod group reduced to 12.5%. Melatonin plays a critical role in the mechanism by which photoperiod affects estrus of female rabbit. Long photoperiod reduces the secretion of melatonin, which promotes the secretion of GnRH in hypothalamus and the expression of GnRH in pituitary. Furthermore, the serum LH, FSH level were elevated, which increasing estradiol secretion, and promoting the development mature of follicles. Finally, it induces the estrus of the female rabbit.