Abstract: The experiment was conducted to investigate the distribution of Orexin B in the hypothalamo-pituitary-gonadal （HPG） axis of 1-month-old Suzhong swine and the sexual maturity sow and its direct biological actions in vitro by immunohistochemical technique and radioimmunoassay. The result showed that Orexin B- immunoreactive neurons localized within the hypothalamus, mainly in the perifornical nucleus (PeF), the lateral hypothalamic area (LHA), dorsomedial hypothalamic nucleus (DMH), and posterior hypothalamic area (PH) and with a sparser distribution in the preoptic, anterior hypothalamic area(AH) and suprachiasmatic nucleus. In pituitary, Orexin B localized in endocrine cell of adenohypophysis pars distalis and intermedia. In gonad, Orexin B distributed in granular cell of primary and secondary follicle and cytoplasm of oocyte, leydig cell of the testis and epididymis. The hypothalamic plants, anterior pituitary cells and granular cell were challenged with 1, 10,100 and 1 000 nmol·L^-1 Orexin B and GnRH, LH and E2 were measured after treatment. Compared to control, 1 000 nmol·L^-1 dose Orexin B significantly increased（P<0.01）GnRH secretion, 100 and 1 000 nmol·L^-1 doses of Orexin B significantly stimulated （P<0.05）LH and E2 secretion These results demonstrated that Orexin B regulated reproduction of porcine in every level of HPG axis.