ZnS nanomaterial,with its surface being respectively modified by polyethylene glycol 4000 (PEG 4000) and oleic acid (OA),is synthesized via hydrothermal method.The impacts of PEG 4000 and OA respectively on the dispersion and suspension properties of ZnS modified lubricant are evaluated by means of ultraviolet spectrophotometer,and the effects of PEG 4000 and OA separately on the anti-friction and anti-wear properties of ZnS nanoparticles as lubricant additives are studied.It is verified that the obtained product is small-size spherical ZnS nanomaterial.Compared with ZnS nanoparticles without modification,the addition of either PEG 4000 or OA makes ZnS evenly disperse in 150SN base oil,and the agglomeration problem is basically solved,thereby improving the tribological properties of lubricant oil.The average friction coefficient and wear scar diameter of lubricant oil decline by 31.56% and 21.33%,respectively compared with 150SN base oil when ZnS/PEG 4000 is used as lubricant additive,those decline 47.12% and 24.75%,respectively when ZnS/OA is used as lubricant additive.