Abstract: To clarify the influence of freeze-thaw process on the thermal conductivity of insulation materials, the changes of water absorption and thermal conductivity of polystyrene（XPS） are obtained by rapid freeze-thaw experiment. Combined with the porous structure characteristics of insulation materials, the thermal conductivity model of three-phase materials is constructed, and the volume fraction correction parameter is introduced to improve the prediction accuracy of the proposed model. Finally, the reliability of the proposed model is verified. The results show that after 200 freeze-thaw cycles, the water content of the XPS increases about 4.55% and the thermal conductivity of the XPS increases by about 43%. By adjusting the two fitting parameters, the maximum relative error between the predicted thermal conductivity and the measured value is less than 5%. The long-term thermal insulation properties of XPS board are influenced by freeze-thaw cycles, so it is of great significance to improve its freeze-thaw resistance. Besides, it is recommended to raise the safety factor of thermal insulation performance to cope with the problems caused by the increase in thermal conductivity of materials.