Abstract: A nano-copper additive is prepared.A series of test such as four ball machine test,anticorrosion test,antiemulsion test and liquid corrosion test were performed to study the anti-wear,anticorrosion,and antiemulsion properties of this additive in hydraulic fluid HL68 base oil.The results show that the nano-copper additive has good performance against extreme pressure and good anti-wear properties in steel-steel friction,as well as excellent anticorrosion property.