Magnetron-sputter deposition was used to produce a Ti-48Al-8Cr-2Ag (at.%) coating on a cast alloy substrate with the same composition. The oxidation behavior of the cast Ti-48Al-8Cr-2Aa alloy and its sputtered coating was investigated in air at 800degreesC-1000degreesC. Hot corrosion was carried out in molten 75% Na2SO4 + 25% K2SO4 at 900degreesC. The results indicated that the oxidation rate of sputtered nanocrystalline coating was lower than that of the cast alloy at 900degreesC. The former formed a scale of merely Al2O3 and the latter formed a scale of Al2O3 + TiO2 mixture. For the same reason, the sputtered nanocrystalline coating exhibited much better hot corrosion resistance than the cast alloy in molten 75% Na2SO4 + 25% K2SO4 at 900degreesC. However, the nanocrystalline showed a little bit higher oxidation rate than the cast alloy at 800degreesC and 1000degreesC, because spherical surface and boundaries or free surface between columnar of the coating gave a larger actual oxidation area than the original alloy.