In order to study the effect of oiliness additives on lubrication performance under full film lubrication,the film thickness and friction coefficient of PAO10(poly-α-olefins)and the PAO10 with mass fraction of 0.2% stearic acid,0.2% palmitic acid and 0.2% myristic acid oiliness additives(denoted as PAOS,PAOP and PAOM,respectively)were measured by using the ball-on-ring film measurement apparatus to study the effect of oiliness additives on the lubricating performance of PAO10 under ball-on-ring contact.The results show that stearic acid,palmitic acid and myristic acid have effects on the film thickness and friction coefficient of PAO10 oil under the condition of full film lubrication.With the increase of entrainment speed,the film thickness increases,but the film thickness of PAOM,PAOP and PAOS is less than that of PAO10.The chain length of oiliness additives in PAOS is the longest and the film thickness of PAOS is the smallest.The slip-to-roll ratio has an obvious effect on the action of oiliness additives,with the increase of slide-to-roll ratio,the shear stress on the oil film increases,which leads to the decrease of the adsorption effect of oiliness agent.The decrease of film thickness and friction coefficient of PAOS,PAOP and PAOM is mainly due to the hydrophobicity of the adsorption film formed by oiliness additives on the surface of steel ball,and the binding ability of the solid-liquid interface reduced with the increase of the molecular chain length of the oiliness agent.