Abstract: Low carbon ZrB₂-SiC/MgO-C composite refractories were prepared after formation, drying, curing and heat treatment at different temperatures (1 373, 1 673 K) for 3 h with magnesia, flake graphite and ZrB₂-xSiC composite powders as raw materials, where x was equal to 0, 20wt%, 40wt%, 60wt%, 80wt%, 100wt%, respectively, and then the effects of SiC content on the physical and mechanical properties of the refractory were investigated. The results show that with the increase of SiC content, the bulk density and rupture strength at ambient temperature of the cured composite refractory increased and then decreased and then increased slightly while the compressive strength decreased in volatility. The performance at ambient temperature of the composite refractory with 20wt% SiC was the best. After heat-treatment at 1 673 K for 3 h, the rupture strength of the composite refractory increased and then decreased with increasing temperature, and the rupture strength at different temperatures all reached the largest values with 20wt% SiC. The change of SiC content had little influence on the relation between load and displacement at different temperatures. The plastic deformation starting temperatures of the composite refractories were 873-1 073 K and the fracture temperature was 1 673 K.