This paper describes the assessment of CFD simulations for the film cooling on the blade leading edge with circular cooling holes in order to contribute durability assessment of the turbine blades. Unsteady RANS applying a turbulence model and the Spalart and Allmaras turbulence model and detached-eddy simulation (DES) based on the Spalart and Allmaras turbulence model are addressed to solve thermal convection. The CFD calculations were conducted by simulating a semicircular model in the wind tunnel experiments. The DES and also the model evaluate explicitly the unsteady fluctuation of local temperature by the vortex structures, so that the predicted film cooling effectiveness is comparatively in agreement with the measurements. On the other hand, the predicted temperature fields by the Spalart and Allmaras model are less diffusive than the DES and the model. In the present turbulence modeling, the DES only predicts the penetration of main flow into the film cooling hole but the Spalart and Allmaras model is not able to evaluate the unsteadiness and the vortex structures clearly, and overpredict film cooling effectiveness on the partial surface.