To evaluate the hightemperature oxidation stability of a ester aviation lubricating oil,the hightemperature oxidation test of the ester lubricating oil under different working conditions was carried out by using the bearing simulation test device to simulate the ultrahigh temperature working condition (above 200 ℃).The viscosity of the oil samples after oxidation was determined,the structure and composition of oil samples was analyzed by liquid chromatography/mass spectrometry(LC/MS)and gas chromatography/mass spectrometry(GC/MS),and the initial oxidation temperature of oil samples was tested by PDSC.The results show that the viscosity of the ester aviation lubricating oil is decreased significantly after high temperature oxidation,which is much lower than that of the initial product.With the increase of simulated temperature,the viscosity of the ester aviation lubricating oil is increased first and then decrease,but the overall change range is very small.The molecular weight of most compounds produced in the oxidation process is higher than that of the original lubricating oil.The oxidation products of oil samples are mainly monoester and diisooctyl sebacate compounds produced after the molecular fracture of the base oil.Through thermal analysis,it is found that under extremely high oxidation temperature(above 200 ℃),the consumption of antioxidant and the production of unstable compound products will lead to a sharp decline in the oxidation stability of oil samples.