The oxidation behavior of an in situ TiB short fibre reinforced Ti-6Al-1.2B alloy was investigated in a flowing air over the temperature range 873-1223 K. The alloy exhibited a parabolic oxidation behavior with the activation energy of 250 kJ/mol, which was supposed to be mainly controlled by the inward diffusion of oxygen. The oxide scales consisted mainly of TiO2, a small amount of Al2O3 and amorphous B2O3. The morphology of TiO2 changed from fine needle-shape at 1023 K to fine sphere at 1073 K and then well-developed block at a higher temperature. The microstructure of the subsurface showed that B2O3 pores and crack appear at the Ti/TiB interface above 1023 K as a result of the oxidation of TiB and evaporation B2O3. Combined with the thermodynamic analysis, it was suggested that the presence of TiB and formation of B2O3 could not act as an oxidation resistance. Finally, the diffusion coefficient of oxygen in Ti-6Al-1.2B exposure to 1073 K in air was determined to be 4.22 x 10(-)11 cm(2)/s.