Abstract: The soft segment of polyether polyols was introduced into the lignin by chemical conjugation, then the lignin-based film was prepared by hot-embossing machine. Their structure and thermal properties were verified by FT-IR, TG and DMA. The effects of the content of lignin, the molecular weight of polyols and the ratio of n_NCO to n_OH on mechanical properties were evaluated. Results showed that the polyether polyols were conjugated to the lignin by urethane bond. The thermal stability was improved and the glass transition temperature was about 72℃. The copolymers exhibited good mechanical properties, under the condition of n_NCO:n_OH of 1.5:1, the mass content of lignin 33% and the molecular weight of polyether polyols 1 500.