Abstract: By considering the moisture-heat coupling mechanism of unsaturated soil under heat source, the double distribution functions are employed to describe the evolution of temperature field and moisture field respectively, and the coupled moisture-heat model is established based on the lattice Boltzmann method. Meanwhile, the corresponding program is compiled to verify the proposed model, using an example of moisture-heat coupling problem in the semi-infinite space. Finally, the evolution of temperature field and moisture field in unsaturated soil are discussed considering the effects of moisture-heat coupling mode, heat source temperature, and soil porosity. The results show that the traditional one-way coupling mode could not characterize the influence of moisture migration on the thermal conductivity of soil, which leads to deviation of temperature field. The proposed two-way coupling mode is more reasonable. The evolution of temperature field and moisture field are greatly influenced by the heat source temperature, and the volume moisture content also changes rapidly at locations where the temperature of unsaturated soil rises fast. Under the same heat source, when the initial volume moisture content is constant, the temperature increases faster for the soil with lower porosity, but the overall difference is not significant, which makes the distribution of volume moisture content very close.