β-solidifying γ-TiAl alloys contain β-phase stabilizing elements such as Mn, exhibiting low cost, excellent hot workability and wear resistance. However, the selective oxidation of Mn during high-temperature oxidation impairs the compactness of the oxide film and deteriorates the oxidation resistance. On this basis, as-cast TMN (Ti43Al1.5Mn3Nb) and TMNW (Ti43Al1.5Mn3Nb-0.4W) alloys were taken as research objects to investigate their oxidation behavior at 850 ℃ and the effect of W addition on oxidation behavior. After cyclic oxidation, the oxidation weight gain (1.34 mg/cm2) and oxide film thickness (11.12 μm) of the TMN alloy are both higher than those of the TMNW alloy (0.98 mg/cm2, 8.12 μm), with no oxide film spallation observed. After isothermal oxidation, oxide film spallation occurs in both alloys, and the oxidation weight gain (3.33 mg/cm2) and spalling mass (6.71 mg/cm2) of TMN are higher than those of TMNW (2.98 mg/cm2 and 4.05 mg/cm2, respectively). The oxide films of both alloys present a four-layer structure: TiO2-Al2O3-TiO3/Al2O3- Mn/Nb/N-enriched the layer. The transition layer between the oxide film and matrix consisted of TiN, Ti2AlN and Laves- (Ti, Nb)(Mn, Al)2 from outside to the inside. The addition of 0.4 at.% W promotes the formation of a compact oxide film, maintaining the stability of the transition layer and improving the spall resistance of the oxide film.