This paper studies the use of Diangu (典故) in Chinese poetry. Diangu (典故) refers to ancient events or stories quoted in poems and words with literary origins (Modern Chinese Dictionary 2012: 290). However, the Western allusion refers to an implicit reference, perhaps to another work of literature or art or to a person or an event; it is often a kind of appeal for a reader to share some experience with the writer; an allusion may enrich the work by association (q.v.) and give it depth (Cuddon 2013: 25). Thus, the concepts of “Diangu (典故)” and “allusion” do not correspond exactly, because the semantic range of the two words are not the same. In order to show the difference, we use the term “Classic Allusion” to refer the Chinese word “Diangu (典故)”. From the cognitive linguistic perspective, Diangu (典故) in Chinese poetry is a category of metaphor (Ji Guangmao 1998 & Bai Minjun 2004 & Zhong Lingli 2009 & Li Pengfei 2010 & Zhang Guowei 2011). Its essence is to use the stories or events that have taken place in history to metaphorize events or people in the present. There are similarities or correlations between these historical events or stories and the events or people in present which form cross-domain projections, and form poetic metaphors based on conceptual blending mechanism, expressing the corresponding metaphorical meaning and emotions. The Diangu (典故) involve both the past (historical events or stories) and present (the present events or people). The “historical events or stories” and the “present events or people” have certain similarities or correlations; both of the mental spaces of the past and present share a same organizational framework. Accordingly, the conceptual blending network of Diangu (典故) belongs to mirror networks. Furthermore, using conceptual blending theory to analyze the internal structure of Diangu (典故) can make readers understand the nature of “Diangu (典故)” more clearly.