Three types of Ti-Al-Nb ternary alloys are obtained by arc-melting and heat treatment, which are γ-TiAl single phase alloy, γ-TiAl + α2-Ti3Al duplex phase alloy, and γ-TiAl +α2-Ti3Al +Nb2Al multiple phase alloy. The phase stability is studied using optical microscope, X-ray diffractometer and electron probe microanalyzer. The oxidation behavior of three Ti-Al-Nb ternary alloys with different microstructures was investigated at 1273K using interrupted oxidation test in air. The compression test was carried out at 298K-1373K. The oxidation resistance of Ti-Al-Nb ternary alloy at high temperature was found to be better than that of the binary Ti-Al alloy. Among the three Ti-Al-Nb ternary alloys, the two-phase alloy with γ+α2 has the best oxidation resistance and mechanical properties. The existence of α2 could enhance the oxidation resistance of the alloy at high temperature. On the contrary, the presence of Nb-enriched phase such as Nb2Al would decrease the oxidation resistance at elevated temperature due to the formation of Nb2O5, which would accelerate the exfoliation of oxide.