Abstract: Take pyrophyllite and carbon black as raw materials to synthesize the Sialon-SiC composites by carbothermal reduction process. Then, apply the composites as additive to unshaped Al2O3-C refractories so as to investigate the effect of heating temperature on the synthesis process and the effect of addition on the properties of refractories. The results show that the composites can be easily synthesized if adding carbon black moderately into pyrophyllite and heating the mixture to 1540°C in nitrogen atmosphere. It is proved that the resistance to oxidation/slag corrosion and hot modulus of rupture of such refractories can be improved obviously if adding moderately the synthesized Sialon-SiC composites into them.