Supercritical carbon dioxide cooled reactor (SCCR) is a new type of gas-cooled reactor with wide application prospects in ship nuclear power, space nuclear power, heating, hydrogen production and other fields. SCCR has many advantages, such as high efficiency, compactness, fast start-up and response speed, low operation noise and so on. SCCR may use the fuel rod design with rib structure. The ribs are used for fixing and mixing. In this paper, the flow and heat transfer of sCO2 in ribbed annuli and smooth annuli are numerically simulated and the results of several turbulence models are compared. The simulation considers the solid-state heat conduction inside the heating rod and the fluid solid coupling at the wall. Simulation results show that the RNG k-ε model has the best performance. The ribs will result in a maximum tangential velocity of approximately 10% of the magnitude of the axial velocity and a larger heat transfer coefficient, but have little effect on pressure drop. Further, the ribs cause periodic changes in turbulent kinetic energy and heat transfer coefficients.