Abstract: The oxidation behavior of TC4 titanium alloy sprayed with boron nitride with different thicknesses under the extreme heating conditions of 660 ℃ and heating time of 1.0 h was studied by spraying boron nitride with air pressure spray gun, and the surface morphologies, cross-sectional thickness and composition of the oxide film were analyzed by metallographic analysis, SEM and EDS microscopic analysis methods, and the oxidation mechanism was discussed. The results show that the main components of the oxide film produced by TC4 titanium alloy under high temperature conditions are Ti O₂ and Al₂O₃, and the thickness of the oxide film produced on the surface of the material without spraying boron nitride is 4.13 μm, and the oxygen content is 29.09 wt%. Boron nitride has a good anti-oxidation effect, in the range of spraying boron nitride thickness of 0.008-0.040 mm, the anti-oxidation effect is proportional to the thickness of sprayed boron nitride; in the range of spraying boron nitride thickness of 0.040-0.051 mm, the anti-oxidation effect is relatively close. The results show that the optimal boron nitride spraying thickness for TC4 titanium alloy is 0.040 mm.