Objective To study the effect of GnRH on the secretion of 5-HT in the stomach. Methods The GnRH-A Alarelin was directly injected into the stomach of rats to observe the change of density of 5-HT immunoreactive positive cell in the stomach and small intestine by immunohistochemical SABC method and 5-HT level in the circulating blood by HPLC-ECD, Results Compared with the control group,which was injected with saline into the stomach,the density of immunoreactive positive cell was significantly increased in the stomach and small intestine in the GnRH-A treatment group;while 5-HT level in the circulating blood was significantly reduced in the experimental group.Conclusion GnRH can inhibit the releasing of 5-HT but not change its synthesis.