Abstract: Annular fuel has two coolant channels, and the change of coolant flow distribution ratio (φ) between external channel and internal channel may affect the heat transfer characteristics of the pellet. In this paper, a fluid-solid coupling CFD calculation model for single annular fuel rod was established. Under four different flow distribution ratio conditions, the influence of the change of flow distribution ratio on the heat transfer characteristics of annular fuel pellet was studied by calculating three evaluation indicators. The calculation results show that the change of flow distribution ratio has no significant impact on the pellet heat transfer characteristics of the annular fuel with a gap structure.