The CaO–MgO–Al₂O₃–SiO₂ (CMAS) corrosion behavior of zirconia-based materials doped with different YO_1.5 contents (8YSZ, 20YSZ, 38YSZ, 55YSZ) and pure yttrium oxide materials (Y₂O₃) at 1300 ℃ has been systematically studied. The results show that the CMAS corrosion behavior of zirconia-based materials with different yttria contents is significantly different. For 8YSZ and 20YSZ with low YO_1.5 content, the corrosion behavior is dominated by solutionreprecipitation and grain boundary corrosion. The former precipitates ZrO₂ grains, while the latter precipitates directly deposited on the surface of the original ZrO₂ to form a core-shell structure. With the increase of YO_1.5 content, the corrosion behavior gradually changed into reactive corrosion. The rapid reaction crystallization of 38YSZ and 55YSZ with CMAS molten salt formed a continuous dense protective layer containing apatite phase, which could effectively block the further erosion of CMAS molten salt. Moreover, the volume fraction of apatite phase in the protective layer formed by 55YSZ was more, which has better corrosion resistance to CMAS. Pure Y₂O₃ samples can also react quickly with CMAS molten salt to form a dense pure apatite layer, which has good corrosion resistance to CMAS molten salt. Therefore, the resistance of thermal barrier coatings to CMAS molten salt corrosion can be controlled by adjusting the yttrium content in zirconia-based materials.