Abstract：Being one of the most important parameters, the rate of thermal conductivity of rock and soil not only decides the distribution of the shallow geothermal field but also constitutes the core of the whole calculation of the heat pump power, thus serving as the key factor affecting the investment on ground-source heat pump projects and the operating energy consumption. Based on a series of experiments, the authors made a full study and statistic analysis of the relationship of the rate of thermal conductivity to water content, natural density and porosity. The test results show that the natural water content increases with the increase of the silty clay thermal conductivity, which can be fitted with the logarithmic and power relationship to obtain the better correlation coefficient. Because the differences in material compositions and microstructures of the samples affect the combination of the heat transfer, it is difficult to indicate the variation trend of the thermal conductivity and water content in the same area with the uniform fitting equations. With the increasing porosity, the rate of thermal conductivity decreases under the condition of constant water content. With the increasing density, the authors obtained the clear trend of increasing rate of thermal conductivity. There are three stages in the variation of rate of thermal conductivity and water content of silty clay. The rate of thermal conductivity increases dramatically when the water content varies in the range of 0-5%. The rate of thermal conductivity increases faster when the water content varies in the range of 5%-20%. The rate of thermal conductivity increases slowly and tends to stabilize when the water content is over 20%.