Abstract: Signaling networks mediated by jasmonic acid (JA) and salicylic acid (SA) can regulate plant defenses responses. Generally, JA-mediated signaling pathways are related to the regulations of anti-herbivore, while SA pathway is concerning defense responses against pathogens. Cross-talk between JA- and SA-pathways plays important roles in fine-tuning defense responses. It is suggested that both jasmonates and salicylates are effectively able to mediate the defense responses of host plant to the parasitism of other plant. This review describes the functions of some defense signaling molecules in plant，especially JA and SA， including their role in responses to insect, pathogen and parasitism. In addition, the application of JA and SA to medicinal plant researches is mentioned.