Animal seasonal reproduction involves complicated neuroendocrine processes of the hypothalamo-pituitary-gonadal axis. It is dominantly regulated by photoperiod, a crucial environmental cue. Melatonin, as internal photoperiod signal, regulates seasonal reproduction of animals. In recent years, it has been found that Kiss1/GPR54 system, which may influence GnRH secretion evidently, is regulated by both melatonin and feedback action of gonadal steroid hormones. Consequently, Kiss1/GPR54 system may play a key role in seasonal reproduction. Additionally, there exists another potential retrograde control pathway of seasonal breeding, which involves TSH-DIO2/DIO3 system. TSH-DIO2/ DIO3 system affects synthesis and secretion of GnRH and is regulated by melatonin, as well as Kiss1/GPR54 system. In this article, melatonin signal, especially the research advances of Kissl/GPR54 system and TSH-DIO2/DIO3 system were reviewed.