To theoretically describe the lowtemperature damping characteristics of vehicular hydraulic dampers and promote the development of highquality damper fluids capable of working under extreme cold weather conditions,firstly,the physical properties of two kinds of highspeed train damper fluids were tested in a wide temperature range of -50~80 ℃,then the calculation errors and limitation when using the regular theories to describe the damper fluid properties were analyzed.A new kind of densitytemperature theory computational formula and a new kind of viscositytemperature theory computational formula based on an improved Vogel formula were proposed, the coefficients in the two proposed formulae were respectively obtained by fitting the tested data in different temperature sections.The comparison of theoretical and experimental results show that the relative calculation error of the new densitytemperature formula is less than 1.4% and that of the new viscositytemperature formula is less than 6%, thus the proposed new models are suitable for describing the physical properties of hydraulic damper fluids in a considerable wide temperature range.