Abstract: Soil thermal parameters are essential parameters in analyzing thermal transfer, and many researches have been focused on finding the simple and accurate estimation method of the thermal transfer parameters. The thermal transfer experiments for four texture soils were conducted through the self-developed experimental system. Thermal diffusivity of four texture soils with different water content and bulk density was calculated. Thermal conductivity was induced by the calculated thermal diffusivity and compared with that calculated by Campbell empirical method. The results show that significant differences exit between thermal conductivity calculated by the two methods. Campbell empirical method was modified according to the experimental results. The modified equation was analyzed, verified and its application scope was discussed. The results show that the modified equation can be used to calculate thermal conductivity in the condition that volumetric water content is less than 20%.