Cr0.82Al0.18N and Cr0.53Al0.47N coatings were deposited on a Ti3Al based alloy by reactive magnetron sputtering method. Hot corrosion of these two coatings in 75 mass% Na2SO4＋25 mass% K2SO4 molten salt at 800℃ was performed in a Setsys 16/18 thermoanalyzer. The phase compositions of the corrosion products were identified by X-ray diffractometer （XRD）. Both the surface and cross-sectional morphologies of the samples were observed by a scanning electron microscope （SEM）. The results showed that both Cr0.82Al0.18N and Cr0.53Al0.47N can reduce the hot corrosion rate of the Ti3Al based alloy and their hot corrosion resistance decreases with increasing aluminum content; the main corrosion products of the coatings are Cr2O3 and 9-Al2O3 and the amount of 9-Al2O3 in the corrosion products is proportional to the Al content in the coating. The better hot corrosion resistance of Cr0.82Al0.18N coating can attribute to the high stability of Cr2O3 in the molten salt.