For the production of high viscosity index lubricating base stock,1decene was used to synthesize poly αolefin with ［Emim］Cl/AlCl3 ionic liquid as catalyst.The influences of AlCl3 and ［Emim］Cl molar ratio,catalyst dosage,reaction temperature,reaction time and reactant water content on the product property and yield were studied.The experimental results indicate that increasing the molar ratio of AlCl3 and ［Emim］Cl or lowering reaction temperature will increase the viscosity of base oil.Excessive catalyst will lead to isomerization of product while increasing the viscosity.Water plays an important role in the degree of polymerization without significant effect on viscosity index of product.When molar ratio of AlCl3 and ［Emim］Cl is 2∶1,catalyst weight is 10%,reaction temperature is 60 ℃,reaction time is 4 h,the synthesized PAO，with viscosity above 10.34 mm2/s at 100 ℃ and viscosity index higher than 143,is ideal to be the base stock of multigrade lube oil for diesel engine.