Abstract: The sub-channel analysis codes merely conduct the analysis on the simple spacer grid, and represent the spacer as the profile drag coefficient, which can only reflect the average effect of the fluid resistance generated by the axial position and can not accurately reflect the effect of mixing vanes on their local field. In this paper, we choose the empirical correlation appropriately and introduce the geometric dimensions of mixing vanes. The term of mixing vane resistance is expressed quantitatively in the axial and lateral momentum equations of sub-channel analysis. Therefore, we establish the distributed resistance of the mixing vanes model. The improved model is applied to sub-channel analysis code, ATHAS. The effect of different shapes, angles or arrangement of mixing vanes of 5×5 bundle assembly is calculated with and without the improved model. Then the thermal hydraulic performance is analyzed accurately, especially the flow and temperature field.