Polyurethane (PU) films were prepared from diphenylmethane diisocyanate (MDI) and polyethylene glycol (PEG) with bean-curd refuse (BCR) as a polyol. Biodegradability of the PU films was investigated in soil and in activated sludge. Biodegradation tests showed that weight loss of PU increased when the content of BCR increased and decreased when the particle size of BCR increased. Morphological observation with a scanning electron microscope (SEM) showed surface damage caused by microorganisms. Thermal and viscoelasitic properties before and after biodegradation tests were measured by differential scanning calorimetry (DSC) and by dynamic mechanical analysis (DMA). Glass transition temperature ( T _g) and dynamic modulus ( E ') of PUs decreased with increasing degradation time. This means that PU main chains were broken by microorganisms.