In chilliness area, the temperature drop of oil in buried pipeline is affected by soil temperature field, and the thermal diffusivity is one of the main of physical property the soil, which affects the temperature drop of oil directly. This paper introduced the test principle of the thermal diffusivity of soil, and researched the influence of thermal diffusivity of soil on the soil physical property, such as soil natural temperature field, soil frozen days, depth of freezing and temperature delay, which can offer theory support for the calculation of hot oil temperature drop in buried pipeline.