The corrosion behavior of a Newly Ni-based superalloy was studied in environments of synthetic coal-ash and synthetic flue-gas at 650 °C and 700 °C for 500 h comparatively. The corrosion kinetics, morphologies, compositions and phases of the corrosion products were characterized by means of SEM, EDS, and XRD, respectively. The results indicated that the temperature is acritical factor in the formation of corrosion layer for the newly Ni-based superalloy. The common denominator is that a dense and uniform layered oxide scales consisting of a Fe2O3 outer layer and an Cr2O3 and Al2O3 inner layer were observed at both 650 °C and 700 °C. The 700 °C high-temperature is the primary cause of the formation of the convex corrosion products and internal sulfide MxSy (M: Cr, Mo). The corrosion mechanism of the newly Ni-based superalloy was also discussed based on the experimental results.