Due to the fast development of aerospace industry, ultra-high temperature thermal insulation materials are urgently requested to resist the drastic aerodynamic heating. At present, ultra-high temperature ceramics (UHTCs) are the best choice owing to their excellent capability at ultra-high temperatures. In this work, highly porous transitional metal carbides were fabricated by foam-gelcasting-freeze drying technology. The strategies of multicomponent modification and realizing superhigh porosity are employed to obtain the high-performance thermal insulator. The research shows that the multicomponent modification greatly decreases the thermal conductivity of porous UHTC. And the superhigh porosity (95.9%-86.4%) could obtain the lightweight sample with the density of 0.38-1.27 g/cm³. Besides, the porous UHTC materials exhibit high strength and improved oxidation resistances. The results highlight the merits of highly porous multicomponent transition metal carbides thermal insulators.