The isothermal oxidation behavior and mechanism of the TiC-TiB2 multiphase ceramics fabricated by self-propagating high temperature synthesis were studied. The result shows that the oxidation kinetics agr ees to the parabolic rule within the temperature rang of RT to 1000℃. First at 600℃ TiB2 was oxidized to be TiO2. Then both TiB2 and TiC were oxidized to be TiO2 when temperature increased to 1000℃. A compact TiO2 film, the oxidation product, formed on the sample surface, which prevented further oxidation and resulted in a very high oxidation resistance of the sample.