Abstract: The attapulgite clay powder is dispersed in 150SN mineral oil as lubricant additive. The tribological properties of steel-steel contacts under the lubrication of 150SN base oil with diversity concentration of attapulgite clay powder are investigated on a standard Optimal SRV-IV tribometer. The elemental component and morphology on worn surface are analyzed by using scanning electron microscopy coupled with energy dispersive spectroscopy. The 150SN mineral oil containing 0.6% attapulgite clay reduces friction coefficient to 57.68% and the wear of steel ball lubricated by 150SN mineral oil containing 0.4% attapulgite clay is 14.52% as low as that lubricated by 150SN mineral oil. Smooth and compact tribofilm composed of oxides is observed on the worn surface lubricated by 150SN mineral oil containing attapulgite clay. The layer-chain crystal structure of attapulgite clay and the complex physicochemical in friction process are responsible for the reduced friction and wear of the tribopair.