The hot corrosion behavior of plasma-sprayed NiCoCrAl-Y2O3 coating on TiAl alloy surface in the mixed melted salt of 75%Na2SO4+25%NaCl at 850 oC for 100 h and the influence of the coating on the anti-corrosion properties of TiAl intermetallics were investigated. The results show that the plasma-sprayed NiCoCrAl-Y2O3 coating could remarkably improve the hot corrosion resistance of TiAl matrix by generating a compound oxide layer of Cr2O3, NiO and NiCr2O4. In the course of hot corrosion, S, carried by Ni, gradually infiltrated into the composite coating and generated a transition product of Ni3S2. Then the partial pressure of the oxygen increased, followed by oxidation which produced oxides including Cr2O3 and NiO. As the amount of the both oxides increasing, the solid-state reaction took place and generated the NiCr2O4 compounds of spinel structure. The transition product of Ni3S2 and the chloridion contained in corrosion media jointly constituted micro-cell, thus accelerating hot corrosion