To analyze a problem of typical blade internal cooling, the periodic case and full spatial case were computed using RANS and large eddy simulation(LES) approaches. The precision of two types of numerical method in predicting flow and heat transfer was compared based on the experimental data published. Numerical research shows that the process of initiation and shedding of the small flattened vortex, which is on the top surface of the rib, was detected by using LES approach, and the phenomenon, that the shedding vortex mixes with other coherent structure when moving along the trace at the height of the top surface of the rib, is accordant with the trend of turbulence intensity variation. The detailed flow structures reflect the true characteristic of the flow and show that not only the parameters of flow condition, including the mean velocity distribution and the turbulent intensity, but also the distribution of enhance factor predicted by LES approach are accordant with experimental data. The prediction error of enhance factor of heat transfer by RANS approach is smaller than that by LES approach.