Polyurethane is a polymer compound that consists of a hard segment and a soft segment. Further modifications of polyurethane make it possible to make foam products with a variety of properties. Polyurethane foam has a tendency to be rigid and flexible by adjusting the segment ratio and adding chain extenders during the synthesis process. The basic precursors used in this research on bio-polyurethane foam are Polypropylene Glycol 2000, Toluene Diisocyanate 80, Amine catalyst, Tin catalyst, surfactant, and the addition of lignin biomass as a chain extender and as independent variables of this study with 1, 2, and 3 wt% variations with the synthesis method used is a one-shot method. In attempt to investigate the effect of lignin chain extender addition to the macromolecular structures and morphology, FTIR and SEM are used, while the mechanical properties are analyzed using tensile machine. From the synthesis carried out, bio-polyurethane foam with open pore shape is obtained. It has increased tensile strength, but the elongation tends to decrease with increasing lignin biomass addition.