Alkyl phosphate modified graphene oxide (GON-DDP) was successfully synthesized using dodecanol, ethanol amine and self-made graphene oxide (GO) as precursors. The structure and morphology of GON-DDP were characterized by FT-IR, XPS, TG/DSC, SEM and TEM. The characterization results indicate that long alkyl phosphate chains were successfully grafted on GO surface, which guaranteed the dispersibility of GON-DDP in hydroisomerization dewax base oil (VHVI8). Then the tribology properties of GON-DDP as friction reduction and anti-wear additive in VHVI8 were evaluated on four-ball machine and SRV test system. The results show that the friction coefficient and wear scar diameter were reduced by 22.7% and 30.3% compared with bare VHVI8 base oil. Moreover, the non-seizure load of VHVI8 was significantly raised by adding GON-DDP. Finally, the lubrication mechanism was proposed according to Raman analysis on the worn surfaces of steel balls.