Abstract: 3D needled C/SiC-TaC composites were prepared by slurry infiltration combined with reactive melt infiltration (RMI). The coefficient of thermal expansion (CTE) of the composites was tested from room temperature to 1400 ℃ using a thermal dilatometer before and after heat treatment. The CTE value of C/SiC-TaC is higher than that of C/SiC composites. The thermal expansion behavior was qualitatively analyzed from thermal stress, preparation method and composition. The results show that the CTE of the composites increases slowly as the temperature increases at low temperature range (below 1100 ℃). The increase in CTE is contributed by the thermal expansion of 90° non-woven cloth, TaC and SiC. The fluctuations of CTE are related to the structural stress, residual silicon and asymmetrical distribution of porosities. In high temperature range (above 1100 ℃), the controlling factors of thermal expansion are 0° non-woven cloth and interfacial thermal stress. The heat-treatment resulted in the decrease in CTE values at temperatures below 1100℃ and also change the CTE behavior of the composites at temperatures higher than 1100 ℃.