Abstract: To meet the high thermal shock resistance requirements of silicon carbide (SiC) pusher plates used in rapid-firing tunnel kilns,the effect of coarse SiC particle content on the microstructure and thermomechanical properties of nitride-bonded SiC composites was investigated. Under a fixed total SiC content, specimens with varying mass fractions (0, 5%, 10% and 15%) of coarse SiC particles (3-5 mm) were prepared. The phase composition, pore structure, flexural strength, elastic modulus, fracture toughness and thermal expansion coefficient were systematically characterized using X-ray diffraction, mercury intrusion porosimetry, three-point bending tests, the single-edge notched beam method and dilatometry. Thermal shock resistance was quantitatively evaluated by measuring the retention rates of flexural strength and elastic modulus after five thermal cycles (water quenching from 1 350 ℃ to room temperature). The results indicated that the coarse SiC particle content significantly influenced the formation of the nitride bonding phase and the resulting microstructure. An optimal content of mass fraction of 5% coarse particles promoted a favorable pore size distribution and a continuous nitride network, whereas excessive coarse particle mass fraction (≥10%) inhibited the nitridation reaction, leading to microstructural degradation. The specimen containing 5%(mass fraction) coarse SiC exhibited the best overall performance, with the highest residual flexural strength (67 MPa) after thermal shock and retention rates of flexural strength and elastic modulus of 16% and 24.8%, respectively. This specimen also demonstrated a low thermal expansion coefficient (4.1×10^-6 ℃^-1) and high fracture toughness (6.38 MPa·m^1/2). It was concluded that the incorporation of 5%(mass fraction) coarse SiC particles achieved an optimal balance between strength and toughness. The enhanced thermal shock resistance was attributed to the synergistic effects of a low thermal expansion coefficient, high fracture toughness and effective crack pinning by the coarse particles.