The steam cooling method was applied in this paper to study the design and characteristics of cooling structure for a vane of gas turbine.The unstructured meshes and realizable k-ε turbulence model were used to study the flow behaviors both inside and outside the grid-ribbed rectangular channel with 15°

30° and 45° rib-roughened wall through 3-Dcoupled numerical simulation.Coupling heat exchange was achieved by heat transfer and solid conduction on the coupled-side of fluid and solid.The cooling medium was steam which had greater Cp and lower viscidity than air.Results show that the flow of the passage is very complex.Heat transfer is enhanced because of the ribs.Ribbed wall has better heat transfer effect than the no rib wall and the cooling effect is obvious.Cooling effect is better by using the steam than by using the air.The numerical result shows the temperature on pressure surface is lower than suction surface.