An increasing interest in re-entry hypersonic vehicles and weapons has driven the demand on the materials for leading edges, nosetips, and propulsion system components. The materials for these applications are exposed to extreme environments including aerodynamic heating which is generated by continuous friction between atmosphere and the materials. To protect the main body of projectiles, the materials used must withstand high temperatures above 3000 oC, thermal shock, and severe oxidation. In this regards, the evaluation of these materials must be preceded before the actual application. An oxyacetylene torch testing is one of the most frequently used methods having the merits of simplicity, low cost, and sufficiently high temperature around 3000 oC. Hf-based ultra-high temperature ceramics (UHTCs) such as HfB2 and HfC have excellent ablation-resistance for relatively long time exposure at high temperature due to those high melting temperature above 3300 oC. Here, high temperature oxidation behaviors of the HfC-SiC and HfB2-SiC composite ceramics are examined using an automated oxyacetylene ablation testing system for 30 min. The post-ablation tested samples are investigated by XRD and SEM.