In order to provide detail data on polyalphaorefin(PAO)’s viscosity for the tribological analysis under EHL lubrication conditions, viscosity-pressure-temperature correlation relation of wide range viscosity grade PAOs (from PAO2 to PAO100) was investigated employing a special compact pressure-generating apparatus called diamond-anvil cell. Pressure-viscosity coefficients were resulted to gradually decrease with increasing pressure and temperature up to 1 GPa at up to 150°C, and the values at 150°C were about a half of those at 40°C for all PAOs. The two representative temperature-pressure-viscosity correlation formulations were well regressed with the high-pressure viscosity data. By substituting the regression formulations for Blok’s pressure-viscosity coefficient, gradually increasing coefficient with viscosity grade were found out, and that of high viscosity PAO100 was about 1.5 times larger than that of low viscosity PAO2.