The thermal resistance of carbon fiber reinforced ultra high temperature ceramic matrix composites (C/UHTCMCs) was characterized by arc wind tunnel testing with heat fluxes of 2, 4.5, and 6.7 MW/m². C/UHTCMCs were fabricated by melt infiltration of an alloy into carbon fiber reinforced carbon composites. Four types of composites were fabricated, each infiltrated with alloys with atomic ratios of Zr:Ti = 20:80, 80:20, Hf:Ti = 20:80, and Zr:Ti:Hf = 80:15:5. The thickness change of the specimens depended on the composition of the infiltrated alloys. Comparison of specimens infiltrated with Zr:Ti = 20:80 and Hf:Ti = 20:80 showed that the specimens containing Hf had a smaller reduction in thickness at each heat flux. The thickness of the specimens infiltrated with Zr:Ti:Hf = 80:15:5 showed the smallest reductions of approximately 1% at 4.5 MW/m² and 7% at 6.7 MW/m². The results of the identification of the scales formed on the specimen surface using X-ray analysis and EDS analysis showed that the scales on the specimen infiltrated with Zr-Ti binary alloy consisted of ZrO₂ solid solution, ZrTiO₄ solid solution, and TiO₂ solid solution. In the Hf-Ti binary alloy infiltrated specimens, the scale was consisted of Hf_xTi_1-xO₂ solid solution. The scale of the specimen infiltrated with Zr-Ti-Hf alloy mainly consisted of Hf_xZr_1-xO₂ solid solution. It was confirmed that the composition of the oxide scale depended on the composition of the infiltrated alloy. The process of oxide scales formation was similar for both specimens. Initially, a reticulate solid phase was formed along the direction of carbon fiber, then a part of the reticulate solid phase changed to the liquid phase, which was dispersed by dynamic pressure. Finally, all the solid phase changed to liquid phase and uniformly covered the specimen surface. The surface temperature of the specimen infiltrated with the Zr-Ti-Hf alloy when overall the solid phase changed to the liquid phase was the highest, at approximately 2500°C. These results indicate that the oxidized specimen formed on the surface of the Zr-Ti-Hf alloy is the most stable. These results suggest that increasing the melting point of the oxide scale formed on the surface and maintaining it prevents specimen recession.