Abstract: The influence of water vapor on the oxidation behavior of GH3600 alloy was studied.The oxidation of the alloy was conducted at 900 ℃in air with different humidity for 24 h by thermal gravimetric analysis system.The oxide surface morphology, cross-section microstructure and chemical composition of the oxide scale were studied after oxidation.The results show that the oxide scales forming under all test conditions are composed of an outer NiO layer and an inner Cr₂O₃ layer.With the introduction of water vapor, the oxidation kinetics and oxide layer structural change significantly.