LaB6-MoSi2-SiC and MoSi2-SiC coatings were prepared on the surface of carbon/carbon composites by pack cementation method. The crystal structures of the coatings were measured by X-ray diffraction. The morphologies and element distributions were also analyzed by scanning electron microscopy and energy dispersive spectroscopy, respectively. The effect of LaB6 on the microstructure and thermal shock resistance of MoSi2-SiC coating was investigated. The results indicated that the LaB6-MoSi2-SiC coating possessed a denser structure and superior thermal shock resistance. After 25 times of thermal cycling oxidation between 1773 K and room temperature, the weight losses of the LaB6-MoSi2-SiC and MoSi2-SiC coated samples were 0.627% and 2.019%, respectively. (C) 2012 Elsevier B.V. All rights reserved.