HfC and TaC are typical ultra-high temperature ceramics (UHTCs), which are important candidate materials for thermal protection components in high-speed aircraft. However, their oxidation resistance at medium and low temperatures is relatively poor. Due to the similar crystal structures of HfC and TaC, and the close atomic radii of Hf and Ta (rHf = 1.585 ?, rTa = 1.457 ?, Δr < 0.15), theoretically, they can form an infinitely miscible substitutional solid solution (HfxTa1–x)C (0 < x < 1). Among them, Hf0.2Ta0.8C has a melting point as high as 4 300 K, which is recognized as the highest melting point carbide. Compared with single-component HfC and TaC, (HfxTa1–x)C exhibits higher initial oxidation temperature and lower oxidation rate, indicating significantly improved oxidation resistance. In this work, a series of processable liquid single-source precursors (SSPs) were successfully prepared by introducing HfCl4 and TaCl5 into allylhydridopolycarbosilane (AHPCS). Through the polymer-derived ceramic (PDC) method, SiC/(HfxTa1–x)C/C nanocomposites with core–shell structured SiC@C and (HfxTa1–x)C@C nanoparticles were obtained, and the evolution of phase composition and microstructure during the ceramic transformation process was investigated.Combining PDC and spark plasma sintering (SPS) technology, nearly dense SiC/(HfxTa1–x)C/C bulk materials were prepared, and the mechanical properties of the resulting bulk ceramic were investigated.