Abstract: The flow heat transfer and cooling characteristics of hydrogen-fired gas turbine were analyzed under coupled action of heat conduction/convection/radiation. A weighted sum of gray gases（WSGG） model was developed to calculate the high ratio of water vapor and carbon dioxide partial pressure. Results show that the increase of water vapor content in the working fluid of hydrogen-fired gas turbine leads to the increase of metal wall temperature. After adding the influence of radiation, the effect of water vapor and carbon dioxide contents on heat transfer is opposite, which is mainly due to the fact that carbon dioxide has a stronger convective heat transfer capacity than water vapor, while water vapor has a stronger radiative capacity than carbon dioxide. Meanwhile, in the hydrogen-fired turbine cooling coupled system with three heat transfer modes of convection-conduction-radiation, the film cooling velocity field is almost unaffected, while the temperature field is deeply affected by coupling effect and radiation. The gas film cooling efficiency under coupled condition defined in this paper can characterize the gas film cooling performance under the condition of hydrogen combustion. Therefore, in the design of hydrogen combustion turbine cooling, the thermal load deterioration caused by hydrogen combustion should be included in the design variables.