Abstract: The effects of void fraction of lubricating oil on lubricating properties, such as film thickness, pressure, non-dimensional fraction force and nondimensional bearing force, of oil-air lubrication are studied by numerical simulation method based on the theory of elastohydrodynamic lubrication. The results show that oil-air lubrication can increase the oil film thickness and expand filmpressure area, the loading capacity is improved by 2%, and the friction force is decreased by 25.8%. Compared with traditional oil lubrication under the same operating conditions, the intrinsic reasons that oil-air-lubrication has advantages over traditional oil lubrication are revealed.