A three-dimensional orthogonal woven C/C-SiC composite was successfully prepared by high-solid-loading slurry impregnation combined with precursor infiltration and pyrolysis. The microstructure, mechanical properties and ablation behavior of the C/C-SiC composite were investigated. The slurry impregnation and the precursor infiltration and pyrolysis acted as fast filling and supplementary densification, respectively. Based on a three-dimensional orthogonal woven C/C preform, the C/C-SiC composite had excellent mechanical properties with bending strength and fracture toughness of 364.46 and 22.86 MPa·m1/2. The mass and linear ablation rates of the C/C-SiC composite were 3.21 mg/s and 4.93 μm/s, respectively, after ablation under an oxyacetylene flame for 300 s. The good ablation performance was attributed to the passive oxidation of SiC at high temperature and high oxygen partial pressure, and the pitting caused by SiO2 accelerated the failure of carbon fibers. [ABSTRACT FROM AUTHOR]