ZrB₂-ZrC-SiC coating with micro-submicron reinforced structure was prepared on the C/C composites by vacuum infiltration and reactive melt infiltration. The micro-submicron reinforced structure consisted of micron-sized SiC as the skeleton and submicron-sized ultra-high temperature ceramic particles (UHTCs) as the filler. The ablation resistance of the composites was tested by plasma flame. Results show that during ablation, the micro-submicron reinforced structure composed of concentrated SiC particles and UHTCs is prone to form larger defects under the erosion of ablative airflow. The defects induce ablation gaps that are connected with the surrounding cracks to form larger pits, which cause part of the coating to fall off, and the failure of the whole coating system.