Abstract: α-SiC ceramics and β-SiC ceramics were obtained by hot-pressing through using Al₂O₃, and Y₂O₃, as sintering additives. The phase composition and microstructure of the sintered SiC were investigated. α-SiC ceramics were densified based on the liquid phase sintering mechanism, in which YAG was formed in situ by the reaction of Al₂O₃ and Y₂O₃. The relatively large grains show that grains grow through solution-reprecipitation and "Core/shell" structure is formed. The phase analysis revealed that the phase transformation ofβ→α in β-SiC ceramics occurred during sintering. The morphology indicated that the rod-like grains were formed in the β-SiC ceramics.