Novel high-temperature thermal barrier materials become the key materials for the development of new generation aeroengines. In this paper, a monoclinic high-entropy rare-earth tantalate material (Y0.2Gd0.2Dy0.2Ce0.2La0.2)TaO4[(5RE0.2)TaO4] was synthesized via solid-state reaction. The thermal, the mechanical and the molten silicate environmental deposits (CMAS) corrosion resistance were investigated. The results indicate that (5RE0.2)TaO4 exhibits a low thermal conductivity (i.e., 1.22 W·m-1·K-1, 600 ℃) and a high thermal expansion coefficient (i.e., 10.3×10-6 K-1，1 200 ℃), Compared with YSZ material (i.e., 2.1-2.7 W·m-1·K-1，100-900 ℃), the thermal conductivity is decreased by 42%. The fracture toughness reaches 2.8 MPa·m1/2, which is superior to most thermal barrier coating materials because of its unique ferroelastic toughening effect. The thickness and penetration depth of the (5RE0.2)TaO4 reaction layer are smaller than those of the YSZ material after being corroded by CMAS at 1 350 ℃ for different durations. This material is a developed thermal barrier coating material with a great application potential.