Abstract: In order to investigate the mixing vane effect on the characteristic of flow and heat transfer under 25 MPa pressure, numerical study was performed with CFX10 in a rectangular channel with a heating rod in center of it, which was modeled from fuel bundles of supercritical water reactor. The results indicate that mixing vane has the distribution of temperature in cross section of channel more uniformly than that without it, and heat transfer is enhanced by the mixing vane.