Lignin is one of the most abundant biopolymers on earth. It has polar and non-polar sides due to its hyperbranched structure, but the polarity of lignin has a higher tendency than non-polarity. Lignin has potential to be compatibilizer if the portion of non-polar can be increased. This research is focused on investigation of the synthesis of lignin-based polyurethane to enhance the non polar portion in lignin. Lignin-based polyurethane was prepared by reacting 4,4'-Methylenebis(cyclohexyl isocyanate) (HMDI) and polyethylene glycol (PEG), then lignin was added to the reaction. In this study, the structure of lignin-based polyurethane was confirmed by NMR and FTIR spectrometers. The NMR and FTIR analyses showed that lignin was successfully grafted. NMR, also used to investigate the effects of molar mass of PEG and isocyanate contents to polarity of lignin-based polyurethane. The polarity of lignin-based polyurethane decreased as the composition of HMDI and molecular weight of PEG increase. This result also occured on the sessile drop test that used to determine surface tension of lignin-based polyurethane. The thermal properties of lignin-based polyurethane was also investigated using STA. Based on STA, enhancement of composition of HMDI and PEG increase thermal degradation and resistance of lignin-based polyurethane.