Abstract: In order to study the influence of porosity and saturation on thermal properties of silty soils, thermal conductivity and specific volume heat of the saturated and unsaturated silty soils from Suzhou and Zhengzhou are measured with the ISOMET apparatus. The evolution relationships between thermo-physical parameters(thermal conductivity and specific volume heat), saturation and porosity are analyzed based on three phase composition of silty soils. The results indicate the thermal conductivity and specific volume heat of silty soils with constant porosity both are increased as saturation increased. The saturation of silty soils has a critical value(S_ro). When the saturation S_r is greater than S_ro, the specific volume heat is decreased as porosity increased. The relationship of porosity, saturation and thermal conductivity is nonlinear and the relationship of porosity, saturation and specific volume heat is linear.