Poly -alpha -olefins synthetic lubricant (PAO)is one of the important synthetic lubricant .The polymerization of C⁸ ～C¹³ alpha -olefins had been studied with boron trifluoride as catalyst .The effects of various kinds of technological condition , such as temperature, pressure , reaction time , various kinds of promoters and mass fraction of the promoter o n the yield of the poly -alpha -olefins synthetic lubricant w ere studied.The optimum technological conditions of poly -alpha -olefins synthetic lubricant are that the temperature is 30 ℃, the pressure is 0 .4 MPa, the reaction time is 4 hours , the promoter is n -butanol, and the mass fraction of the promoter is 0.1 %.Under the optimum technological conditions, enlarge experiment of poly -alpha -olefins synthetic lubricant was carried out with 10 L reactor .The proper ties of the poly -alpha -olefin synthetic lubricant w ere studied.The yield of the poly -alpha -olefins synthetic lubricant is 81 .42 %.The results show that the viscosity at 100 ℃ is 4 .87 mm²/ s, the viscosity at 40 ℃ is 21 .15 mm²/s , the viscosity index is 126 , the condensation point is -62 ℃.The pro ducts of synthetic lubricant have low viscosity ,low condensation point and high viscosity index .This work provides a fundamental data for studying the poly -alpha -olefins synthetic lubricant in industry .