The effects of various basic factors of combustion gas flow conditions on the recession behaviors of silicon carbide and alumina have been experimentally clarified. The exposure tests were performed under various gas flow conditions (T=1100∼1500°C, P=0.3∼0.7 MPa, V=45∼250 m/s, PH2O=30∼120 kPa and PO2=22∼43 kPa). The recession rate of silicon carbide mainly depended on water vapor partial presssure, temperature, and velocity in combustion gas flow. The pressure dependence was not found and the oxygen dependence was extremely low. Alumina also showed linear weight loss and the surface recession, and water vapor partial pressure, temperature, and velocity dependences were observed. It was considered that the recession of Al2O3 occurs in order to volatilize by forming gaseouse hydroxide species, as same as SiC. The recession rates of silicon carbide and alumina in combustion gas flow were experimentally expressed in the form exp(- E/RT)PH2OxVy.