While observing the research history of epics, we would find researchers have paid close attention to the origin, development and changes of epics, and paid little attention to the decline of epics. In the article, the author argues the study of decline of Jangar has theoretical and practical importance to understand the vanishing history of dead epics, to understand the necessity of cherishing and spreading the existing oral tradition. Previous studies on the life-cycle history of Jangar mainly concentrated on the its origin and formation, and neglected the issue of its decline and extinction. Therefore, the decline and extinction issue of the Jangar oral tradition should become an important part of Jangar studies, which is as important as the origin and formation issue, and is theoretically significant in preservation of the Jangar oral tradition. The study deals with the decline and extinction of oral traditions of minorities in China, and plays an important role in the preservation and inheritance of living oral traditions as well. It would provide valuable reference materials to understand the life-cycle history of already extinct epics including Greek ones.