Terahertz timedomain spectroscopy was used to study the low temperature feature of lubricating oils.The terahertz timedomain spectrum of several kinds of lubricating oils from -40 ℃ to 0 ℃was measured in the selfbuilt transmission terahertz timedomain spectroscopy system.The absorption coefficient and refractive index of the lubricating oils were obtained by processing the terahertz timedomain spectrum.The results show that low temperature leads to the crystallization of hydrocarbons in lubricating oils,and the increasing of viscosity and the loss of fluidity.It shows the time delay increasing in the Terahertz timedomain spectroscopy by influence of temperature decreasing in lubrication oils,and there is certain regularity between the temperature and time delay.The decrease of the temperature leads to the increase of the refractive index and the absorption coefficient of the lubricating oils,and relativity is also shown between temperature and refractive index.Terahertz timedomain spectroscopy can detect the effect of temperature change on lubricating oils very effectively,and can be used to study the low temperature performance of lubricating oils.