Abstract: The byproduct of sulfite pulping, namely sodium lignosulfonate was used as raw material in this study, and the influences of reaction conditions such as cooking temperature, time and the content of NaOH to the desulfonation of sodium lignosulfonate were studied using uniform design. The results indicate that the optimal desulfonation condition is as follows: cooking at 180℃ for 3h with 7% NaOH. Lignin, which is obtained from desulfonation of sodium lignosulfonate, has good glass, transition property, thermoplastic property and heat-plasticity through the analyses of IR spectra, GPC(gel permeation chromatograms), TG-DSC and rheological analysis. The research provides the academic reference for the exploitation and utilization of thermoplastic lignin.