Soil thermal conductivity is an essential parameter for studying the coupled transport of heat, water, and solute at land surface. It is generally recognized that soil thermal conductivity is increased at elevated temperatures due to the enhanced latent heat transfer. The objective of this study was to develop a model that was capable of predicting soil thermal conductivity at high temperatures. The gas diffusion law was applied and the latent heat transfer of vapor was introduced to a soil thermal conductivity model for moderate temperature. The performance of the model was examined by heat-pulse measurements of soil thermal conductivity at various temperatures and water contents. The results indicated that the vapor enhancement factor varied with soil texture and existed a great uncertainty. Thus the parameters of Cass et al that were used to estimate the vapor enhancement factor were modified. When the adjusted parameters were applied, the new model was able to predict soil thermal conductivity accurately at high temperatures.