Thermal barrier coatings (TBCs) are one of the core thermal protection technologies for the hot components of advanced aeroengines. Under high−temperature service conditions, TBCs of engine blades are eroded and damaged by environmental deposits mainly composed of CaO−MgO−Al₂O₃−SiO₂ (CMAS), leading to early spalling and failure of the blade coatings, which has attracted extensive attention in the field of high−temperature protection among the researchers. Especially for the commonly used TBCs material−yttria−stabilized zirconia (YSZ) prepared by electron beam−physical vapor deposition (EB−PVD) method, molten CMAS can easily penetrate into the coatings through the columnar crystal gaps and microcracks, causing severe corrosion. This article focused on the urgent issue of CMAS corrosion in the high−temperature service process of TBCs for advanced aeroengines. A proper amount of Al₂O₃ was doped into the YSZ material by means of composition modification to form an Al₂O₃−YSZ composite coating (AYSZ coating). YSZ coating and AYSZ/YSZ coating were fabricated on the surface of alumina ceramic plates by EB−PVD technique. The phase composition and microstructure evolution of the coatings were studied. The comparisions of the two coatings were made on their thermal conductivity, high−temperature thermal stability and resistance to molten CMAS. The results show that in the AYSZ/YSZ coating system, YSZ possesses feather structure while AYSZ exhibits "micro columnar crystal" structure at the microscopic level. Compared to YSZ coating, the porosity of AYSZ coating decreased by 12.6%, indicating that AYSZ is denser layer. The thermal conductivity of AYSZ coating at 1200℃ is only 0.94 W/(m·K), which is better than that of YSZ coating at the same temperature. Moreover, it maintains phase stability for a long time at 1400℃ and has excellent high−temperature stability. AYSZ coating exhibits certain resistance to melting CMAS corrosion, which is because of its dense "micro columnar crystal" structure, as well as the reaction sacrificial layer containing high melting point compounds such as CaAl₂Si₂O₈, MgAl₂O₄, and CaAl₄Si₂O₁₁ formed by the reaction between AYSZ coating and CMAS, hindering the penetration of CMAS into the interior of the coatings. The novel developed AYSZ coating has achieved efficient insulation, high−temperature stability, and resistance to molten CMAS corrosion, providing theoretical and technical guidance for the development of long−life and corrosion−resistant TBCs for aeroengines.