Abstract: The corrosion behavior of commercial Ni-base alloy materials 263 and 282 in a simulated environment of flue gas at 700-800 ℃ from coal-fired boiler was studied. The weight change of Ni-base alloys after corrosion was calculated, and a scanning electron microscope-energy dispersive spectroscope (SEM-EDS) was used to analyze the microtopography of the corroded alloys. Results show that the corrosion behavior of Ni-base alloys includes three mechanisms: oxidation, sulfidation, and sulfate corrosion. The corrosion rate is controlled mainly by sulfate corrosion. The molten sulfate eutectics lead to general corrosion of the Ni-base alloys, thus the alloy matrix is dissolved continuously at an approximately constant rate, and the weight loss of the alloy increases first and then decreases with the increase of temperature. Meanwhile, sulfur diffuses into the alloy matrix and results in local sulfidation. The low-melting metal sulfides melt down which might lead to formation and propagation of internal cracks in the alloy. The increase of temperature will significantly aggravate the sulfidation corrosion of Ni-base alloy.