Ablation behavior of 3D C/ZrC–SiC composite was tested under an oxyacetylene flame and an ablation mechanism was proposed. A five-layer microstructure formed after ablation, including the ZrO 2 -melting layer, the porous layer, the SiO 2 -rich layer, the SiC-depleted layer and the composite substrate. The ablation rate is controlled by oxidations of carbon fibers, SiC and ZrC in the first stage, and then controlled by the scouring away of ZrO 2 –SiO 2 binary melt by gas flow and the oxygen diffusion through the glassy ZrO 2 –SiO 2 layer. Finally the evaporation of SiO 2 controls the ablation rate cooperative with the last mentioned two ablation behavior.