This paper reports the outcome of our research for resolving the very severe disagreement between the computed and measured results of the 90 deg duct flow with strong curvature. Three kinds of turbulence models (standard k- eddy-viscosity turbulence model, RNG k- model and RNG k- model with C μ modification) have been used to predict the abovementioned flow. The results demonstrate that RNG model and the revised model can provide satisfactory computed results. Both of the mean velocities and Reynolds shear stresses are in quantitiative agreement with the experimental data. We feel that the RNG k- model suggested in this paper can be a useful turbulence model for practical engineering and scientific computations.