As one of the most renowned and sensational classics in the history of modern Chinese literature, Fortress Besieged has been under the spotlight ever since it was published in 1947, about which researches in various academic fields keep on emerging and flourishing unceasingly, transcending time and space. Given the truly delightful fact that Fortress Besieged is distinguishingly abundant in metaphors, this article attempts to analyze some classically representative metaphors in this novel from the perspective of Conceptual Metaphor put foreword by Lakoff and Johnson, which consists of three closely interrelated components, namely, structural metaphor, ontological metaphor, and orientational metaphor. A conclusion has been drawn that conceptual metaphor is realized in virtue of mapping between the source domain and target domain, which specifies the abstract, familiarizes the strange, and acquaints the unknown. In addition, the application of metaphor in Fortress Besieged highlights not only the linguistic art of literary works but also reflects the author's original thinking pattern.