Abstract: A phases diagram of predominance area of the Si-C-O system at 1530°C was plotted according to the correlative thermodynamic data. Then, the SiC-ZrO2 composite was synthesized via a carbothermal reduction reaction at 1530°C for 4 h in argon atmosphere, with zircon and carbon black as starting materials and La2O3 reagent as additive. Phase composition and microstructure of the synthesized composite were characterized by XRD and SEM. The results indicated that the increase in additive mass fraction is beneficial to the decomposition of ZrSiO4 and the formation of SiC. It was found that the mass fractions of ZrO2 and SiC in the sample come to the max. values, i.e., 82.8% and 10.8%, respectively, if that of w (La2O3) is 2%. The grain shapes of SiC in the sample are mostly granular and acicular with an average grain size about 200 nm.