In view of the problem that the pressure of lubricating oil system drops obviously and fluctuates obviously after a domestic aviation lubricating oil replaces the imported aviation engine lubricating oil 50-1-4Ф,the roller bearing simulation test device was used to compare the foam characteristics of the imported and domestic aviation engine lubricating oil.The difference of high temperature anti-foaming performance between the two lubricating oils and their lubricating base oils,polyalphaolefin (PAO) and diisooctyl sebacate(DOS) were investigated.The results show that at the same oxidation temperature,the anti-foaming performance of the domestic aviation engine lubricating oil and its lubricating base oils of PAO is obviously worse than that of the imported aviation lubricating oil 50-1-4Φ and its lubricating base oils of DOS.The change trend of antifoaming performance of two kinds of product oils and their base oils is basically the same under different oxidation temperature,which shows that the antifoaming performance of lubricating oil mainly depends on its base oil.Therefore,the problem of unstable oil pressure in domestic aviation lubricating oil is probably caused by the poor antifoaming performance of the nonpolar base oil PAO used by the domestic aviation engine lubricating oil compared with polar base oil DOS used by the imported aviation engine lubricating oil.