Fully dense SiC bulks with Al2O3 and Al2O3 + Y2O3 sintering additives were prepared by spark plasma sintering and the effect of sintering additives on the hydrothermal corrosion behavior of SiC bulks was investigated in the static autoclave at 400 degrees C/10.3 MPa. The SiC specimen with Al2O3 sintering additive exhibited a higher weight loss and followed a linear law. However, the SiC specimen with Al2O3 + Y2O3 additive exhibited a lower weight loss and followed a parabolic law, indicating that the corrosion kinetic and mechanism were different for these two SiC bulks. Further examination revealed that, a deposited layer was formed on the surface of SiC specimen with Al2O3 + Y2O3 sintering additive after corrosion, which can effectively protect the SiC specimen from further corrosion, and thereby improved the corrosion resistance of the SiC specimen with Al2O3 + Y2O3 sintering additive.