Cyclic oxidation behavior at 750-850 °C was investigated for Ti42Al1.5Mn3Nb0.1B and Ti42Al1.5Mn- 3Nb0.1B0.2C0.2Si alloy by using scanning electron microscopy, electron probe microanalysis, electron backscatter diffraction and X-ray diffraction analysis. The kinetic curves for both alloys roughly follow a parabolic law, with the reduced oxidation rate constant compared to that of Ti42Al5Mn1W alloy at 800 °C. Well-protected oxide films are generated on both alloys at all experimental temperatures, without cracking or spalling of the oxide layer. The addition of Nb inhibits the growth of TiO₂ and promotes the selective oxidation of Al to form a dense and protective Al₂O₃ layer. What is more, the addition of trace Si further promotes the oxidation resistance of the alloy, prompting the alloy to generate a denser alumina layer, which further inhibits the internal diffusion of O and reduces the oxidation mass gain, and this effect is more significant at higher temperatures.