In order to determine the relationship between the property of MgOAl2O3SiO2 composite ceramics and molar ratios of MgO/Al2O3, especially the sintering behavior and thermal shock resistance, the MgOAl2O3SiO2 composite ceramics were fabricated with micro-size MgO, Al2O3 powder and nano-size SiO2 as main raw materials. The sample was characterized by phase analysis, densification and thermal shock times. Moreover, field emission scanning electron microscope was also conducted to study microstructure of the samples before and after thermal shock. Effect of different molar ratios of MgO/Al2O3 on the sintering behavior and thermal shock resistance of composite ceramics were investigated. The results showed that the sample possess better sintering behavior and thermal shock resistance with the molar ratio of MgO/Al2O3 equal to 2/1. Grains of periclase and spinel were directly bonded together, resulting in a dense and compact microstructure, and the bulk density of obtained sample reached 3.4 g/cm(3). The microstructure of sample after thermal shock revealed that the crack propagation path was deflected and bifurcated, the main-crack propagation was restricted and more fracture energy was consumed, the thermal shock resistance of composite ceramics was greatly improved. (C) 2016 Elsevier B.V. All rights reserved.