This study used the Al2O3 nano-lubricant produced from the direct synthesis method was used as the experimental samples and the ultrasonic vibration was used for dispersing the nanoparticles into three types of the weight fraction (0.1, 0.2, 0.3%wt). The base solvent was the lubricant of vacuum pump. The objectives of this study were to discuss the dependence of operating temperature of vacuum pump under the various weight fraction of Al2O3 nanoparticles. In this experiment we added Al2O3 nano-lubricant into the direct drive oil sealed rotary vacuum pump, and used the thermocouple measure the temperature on the four test points (cylinder, in-lubricant, case of vacuum pump and discharge pipeline). The results show that the cylinder temperature was reduced by 1.3% and increased by 0.4%, 1.8%, the lubricant temperature was increased by 5.3%, 0.5% and 1.9%, the case surface temperature was reduced by 1.7%, 1.4% and 1.5%, and discharge pipeline temperature was reduced by 0.6%, 2.1% and 3.8% respectively when the sample fractions were 0.1%, 0.2% and 0.3%wt. From the results, it could be realized that the nano-lubricant has more effects on increasing the performance of heat sink than conventional lubricant.