Abstract: The surface temperature of the first stage turbine blade of a heavy-duty gas turbine was measured in a high temperature wind tunnel by using infrared thermography technology, and the surface cooling efficiency distribution formed by steam and air cooling was compared and analyzed. A conjugate heat transfer-computational fluid dynamic（CHT-CFD） work of the cooling blade was also performed for analyzing the cooling performance of other coating surfaces and all the coating substrate surfaces. Results show that local cooling efficiency on blade coating surfaces and their substrate surfaces cooled by steam and air present almost the same distribution characteristics. The heat insulation effect of the thermal barrier coating（TBC） is more obvious when it is cooled by steam. Given the same consumption of coolant, the cooling efficiency of the pressure surface and its substrate surface of the blade coating increased by 23.9 and 25.5 percentage points respectively compared with that of the air cooling, and for the suction surface, the improvement are 17.3 and 21.7 percentage points respectively.