The Yi people''s epic History of Yelang is a hand-copied family heirloom of the famous "Mangbu Bimo" family in the Wumeng Mountain area and has distinct characteristics of the integration of written and oral traditions. By analyzing History of Yelang using oral formula theory and Yi poetics theory, the preservation and changes of oral traditions in the written text of the epic are discovered. The preservation of oral traditions by the epic is mainly reflected in the tripartite narrative, formula, and story pattern of the epic. The changes are manifested in the epic''s inheritance of Yi poetics and the written adaptation of the quoted folk oral stories in text compilation, weakening their legendary colors and making the epic closer to "historical record"