Abstract: To illustrate the evaluation laws of thermal and mechanical properties of lignin-treated silt during curing period, a series of laboratory tests including standard proctor compaction test, thermal resistivity test, unconfined compressive strength test, modulus of resilience test, mercury intrusion porosimetry and scanning electron microscopy analysis are conducted to study the relationship among thermal resistivity, strength and stiffness and lignin content, moisture content and curing time of treated silt. Moreover, the changes of microstructure of lignin-treated silt are qualitatively or quantitatively evaluated to state the relationship between thermal and mechanical properties of treated silt. The test results show that the maximum dry density of treated silt is higher than that of natural silt, but the optimum moisture content is lower than that of natural silt. The sensitivity of the dry density to changes of moisture content increases. The thermal resistivity of treated silt increases nearly with the increase of lignin content and curing time, and after 60 days of curing all the treated soils, the thermal resistivity tends to be the same. It is closely related to the density of soils and the thermal properties of soil compositions. The strength of treated silt increases with the increase of lignin content and curing time and are 6.0 times higher than natural silt for 12% lignin treated after 28 days of curing. The variation of modulus of resilience for treated silt is similar to that of the unconfined compressive strength. The optimum content of lignin for treating silt is approximately 12%. The total pore volume and average pore diameter of silt are significantly reduced, and a more stable soil structure is formed by coating, connecting particles and filling pores after treatment of lignin.