Abstract: This paper,by employing some theories form pragmatic,aims to discuss the rhetorical device of irony when used in oral English.The introduction is a simple explanation of the concept and history of irony.The main part concerns three aspects of irony-the form,the effect and the components.In conversation the irony may show itself in such different ways as verbal irony,situation irony and quotation irony,which can always reinforce the emotion of sarcasm or humor when there are some special factors in communication,such as the cooperative speaker,the understanding listener,the meaningful words,the indispensable environment and so on.The last part is a clean summary of the whole paper.