Abstract: Mixing vanes installed in the spacer grids are significant structures of fuel assemblies in nuclear reactors, and the behavior of which has vital effect on the thermal-hydraulic characteristics of the fuel rod bundle channel. Numerical analysis of the effect of the vane arrangement and the vane tip shape was carried out to investigate the 5×5 rod bundle with single-span spacer grid. The results showed that the pressure drop was almost unaffected by the arrangement of the mixing vane, while the flow pattern and heat transfer characteristics downstream of the spacer grids varied evidently as the arrangement changed. As the shape of the vane tip changed into an arc, the pressure drop was not significantly different from that of the typical one, but the heat transfer characteristics was obviously improved.