Abstract: In order to improve the melting property of soda lignin and prepare soda lignin-based fibers by melt-spinning, soda lignin isolated from black liquor was heated with polyethylene glycol-400 (PEG-400) at different mass ratios and then poured into water with different stirring time, followed by filtration and drying. The thermostability and viscosity as well as melt-spinning property of treated soda lignin were determined. The conclusions are obtained as follows. 1) Within the same stirring time, there was little effect of mass ratio on the ash content, but lignin content decreased with the increase of mass ratio; at the same mass ratio, longer stirring time resulted in the less ash content and higher lignin content. 2) The decomposition temperature of soda-lignin increased after the treatment with PEG-400, but it decreased with the increasing mass ratio or stirring time. 3) Poor melting properties were observed from the soda-lignin treated by PEG-400 at the mass ratios of 1:1 and 1:2, while the soda-lignin treated by PEG-400 at the mass ratio of 1:3 showed good melting property. Especially for the stirring time of 2h, soda-lignin exhibited stable melting property and could be processed into lignin-based fibers with the average diameter of 30±4.8μm by melt-spinning at the temperature of 228℃.