Abstract: By analyzing their mineral compositions, the thermo-physical properties of 4 kinds of red clay in Guangxi Province are studied from the perspective of soil mechanics. The relationship between the thermal parameters and their impact factors also discussed. The results show that the thermal conductivity and specific heat capacity both increase linearly with the increasing water content when the dry density of soil samples keeps the same value. There is a critical water content point on the change curves of thermal conductivity. The thermal conductivity increases sharply in a line with the increasing water content when the water content is lower than the critical point. Conversely, the thermal conductivity increases slowly and tends to a stable constant. The thermal diffusivity increases with the water content when the water content is lower than the critical value. However, the thermal diffusivity decreases with the water content when the water content is larger than the critical value. The change curves of thermal diffusivity are shown as parabolic shape. It is also found that the thermal conductivity, specific heat capacity and thermal diffusivity show a linear increase with the dry density when the soil water content keeps the same value. Finally, the quartz content of mineral composition of red clay has obvious impact on its thermal conductivity. The increase rate of thermal conductivity of red clay is positively related with its quartz content.