Simplified rectangular or square channels are commonly adopted for studying turbine blade internal cooling characteristics under constant temperature or constant heat flux boundary conditions, but the effects caused by those simplifications have not been considered in detail. This paper used a numerical method to study blade internal cooling in a realistic rib roughened two-pass channel of a Pratt & Whitney Energy Efficient Engine high-pressure turbine blade under turbine design conditions. The purposes are two-fold: 1) to investigate the effects of the types of wall boundary condition on blade internal heat transfer, including coupled wall, constant temperature wall, and constant heat flux wall; 2) to present the internal heat transfer and pressure losses in the channel with two types of rib roughened walls, i.e., Model A with 60-degree inclined ribs and Model B with 60-degree V-shaped ribs. Both stationary and two rotating conditions with rotation number Ro= 0.1 and 0.2 are considered. The turbulence model is Shear Stress Transport k-ω model. The results revealed that: 1) The types of wall boundary conditions have large effects on blade internal cooling performance. At the stationary condition, the maximum difference in local normalized Nusselt number (Nu/Nu0) on the trailing surface can be as large as 44.4% between the coupled wall and constant temperature at the inlet pass, and 50% between the coupled wall and constant heat flux at the outlet pass. Under blade rotations, the large difference in Nu/Nu0 remains on the trailing surface, while on the leading surface only minor difference exists. 2) At the stationary condition, the maximum difference in Nu/Nu0 between the trailing surface and leading surface for Model A 51.3%, and Model B 40.7%. 3) At the stationary condition, in the inlet pass, the results of Mode A and B are close to the simplified channels. In the outlet pass, a relatively large discrepancy exists between the two ribbed models and their corresponding simplified channel results. 4) Blade rotation results in a large increase in Nu/Nu0 on the trailing surface in the inlet pass and bend regions of the three models. The maximum change in Nu/Nu0 reaches over 100% for each model, which is significantly higher than that of the simplified channels. 5) The friction factor of the two ribbed models decreases with the rotation number. The difference in pressure drop and friction factor between the two ribbed models also decreases with the rotation number.