Four polystyrene microspheres with different monomer addition were synthesized by the method of dispersion polymerization,and the properties of polystyrene microspheres were characterized by SEM,TGA,DSC and IR,and the optimum addition of styrene monomer was screened.The polystyrene microspheres with different concentrations were added to the regenerated base oil,and the dispersion and tribological behavior of oil samples were detected by UV visible spectrophotometer and four ball friction tester.The antiwear and friction reducing mechanism of microspheres under different loads was discussed.The results show that when the styrene monomer dosage is 18 mL,the synthesized microspheres have the best effect.Polystyrene microspheres show excellent friction reducing and anti-wear effect in the regenerated base oil,which can reduce the friction coefficient by 7767% and the wear scar diameter by 273% at the optimum addition of 030%(mass fraction).At low load,he friction coefficient curves of regenerated base oil with polystyrene microspheres is relatively stable,and is generally smaller than that under high load,which indicates that polystyrene microspheres are more suitable for use at low load.This is because the microspheres play a “ball” role on the friction surface under low load,while the microspheres only play a sliding role under high load.