The preparation and characterization of ceramic/ceramic composite of reaction bonded mullite-silicon carbide composite was investigated. The samples were formed by using silicon carbide (SiC) powder and aluminium oxide (Al2O3) as starting materials and carboxymethyl cellulose (CMC) as binder. The uniaxial press and cold isostatic press were applied in forming precess. Sintering was carried out at 1450 ํC and 1500 ํC in air atmosphere. During reaction bonding process to form mullite, SiC were oxidized and formed SiO2 layer on its surface. This process is so called passive oxidation. The activation energy for oxidation of SiC calculated by Arrhenius's equation was about 167 kJ/mol. It was also found out that the amorphous SiO2 excess was formed and covered up the porosity in sample. Porosity obtained in the sample is about 10 vol.% and three point bending strength of sample around 60 MPa.