It is increasingly appreciated that neuroendocrine-immune interactions hold the key to understand the complex immune system. In this study， we explored the role of a reproductive regulation-related hormone， GnRH， in the regulation of immunity in Hong Kong oysters. We found that vibrio bacterial strains injection increased the expression of ChGnRH. Moreover， ChGnRH neuropeptide promotes the phagocytic ability and bacterial clearance effect of hemocytes which regarded to be the central immune organ. The content of cAMP after incubation with ChGnRH peptide was increased， which could be blocked by adenylyl cyclase inhibitor SQ 22，536. Furthermore， the stimulated effect of ChGnRH peptide on the phagocytosis and bacterial clearance was also blocked by SQ 22，536， H89 and enzastaurin， strongly demonstrating that cAMP dependent PKA and PKC signaling pathway was involved in ChGnRH mediated immune regulation. In conclusion， this study confirms the presence of neuroendocrine-immune regulatory system in marine invertebrates， which contributes to understand the complexity of oyster immune defense system.