Dynamic property of polyurethane foam is investigated experimentally. Polyurethane foam is loaded periodically with various amplitudes and various frequencies, and load, deflection and velocity of the polyurethane foam are measured. Using non-parametric identification technique in time domain, dynamic property of polyurethane foam is modelized as a function of velocity and deflection of polyurethane foam. Then we proposed a new model of dynamic property of polyurethane foam. Experiments are conducted with various conditions of size and compressibility, and the validity of the proposed model is confirmed. Difference of dynamic property by size and compressibility is investigated.