The Al 2 O 3 -ZrO 2 (3Y)-SiC composite ceramics used in solar thermal power were prepared by micrometric Al 2 O 3 , nano-ZrO 2 and SiC powders under the condition of pressureless sintering. The bulk density and bending strength of samples with 10vol% nano-ZrO 2 sintered at 1480 ℃ were 3.222 g/cm 3 and 160.4 MPa, respectively. The bending strength of samples after 7 times thermal shock tests (quenching from 1000 ℃ to 25 ℃ in air medium) is 132.0 MPa, loss rate of bending strength is only 17%. The effect of nano-ZrO 2 content on the microstructure and performance of Al 2 O 3 -ZrO 2 (3Y)-SiC composite ceramic was investigated. The experimental results show that the bending strength of samples with above 10vol% nano-ZrO 2 content has decreased, because the volume expansion resulting from t-ZrO 2 to m-ZrO 2 phase transformation is excessive; Adding proper nano-ZrO 2 would be contributed to improve the thermal shock resistance of the composite ceramics. The Al 2 O 3 -ZrO 2 (3Y)-SiC composite ceramic has promising potential application in solar thermal power.