Metonymy, one of the human's most fundamental cognitive patterns, is often found in languages apart from the metonymy of an entity. Distinct from semantic implication, pragmatic inference, and special name, event metonymy has the characteristics of the mutual independence between cognitive domains, the contingency of mapping, and the reducibility of the source domains. The basic types of event metonymy are the metonymy of event elements and that of relevant events. The former type is a part of an event, and the latter one invokes the mechanism of the qualia structure. In conclusion, the generation of event metonymy is bound by the discourse restrictions, which include the demonstrative disparity and the tendency to informal discourse.