Composition for preparing a biodegradable polyurethane-based foam and a biodegradable polyurethane foam, comprising mixtures based on poly(hydroxybutyrate) polymer, polyols of renewable source, isocyanates and additives, with the object of preparing biodegradable polyurethane foams. In the process, the poly(hydroxybutyrate) plus the polyol, the isocyanate and the additives are previously mixed in specific mixers; once the homogenization is reached, the mixture is poured in mold for growing. After curing, the resulting product presents foam characteristics, with its density, toughness and cell size varying according to the proportion of the reagents and allowing the manufacture of several products.