The low viscosity poly-α-olefin synthetic base oil was prepared from 1-decene. The effects of conditions and the catalyst on the poly-α-olefin synthetic base oil were studied, such as the molar ratio between anion and cation, the content of catalyst, reaction temperature and reaction time.The molecular structures of PAO were characterized by IR, and the physical and chemical properties were tested by flash point apparatus, etc. The thermal stability of PAO was analyzed by TA. The results showed the better experimental conditions, they were,the molar ratio between ［Bmim］Cl and AlCl3was 1.0:2.5,the mass fraction of catalyst was 7％, the reaction temperature was 80℃ and the reaction time was 4h. The synthesized PAO was of excellent physical properties, chemical properties, and thermal stabilities, which had long side-chain and regular structures.