Abstract: Adopting various meshing strategies,numerical calculation of internal turbulent flow in long straight circular pipes is proceeded by the FLUENT software.Comparison between calculated results and curves of semi-empirical expressions shows that the numerical solution is effected by mesh size,ratio and the y⁺ value of the near-wall grid that plays a crucial role in the effect.At the same model and identical meshing strategy,different boundary condition leads to different accuracy of the result.Otherwise,different model will not cause significant difference in accuracy at the same boundary condition and meshing strategy.Thus,suitable meshing strategy especially the near-wall grid size should be selected to adapt to different boundary condition.