Damping and elastic properties of binary powder mixtures were investigated by a dynamic measurement method using vibration. Experiments were performed on a range of binary powder mixtures comprised of glass sphere, sand, polyethylene and rubber powders. Loss factor and Young's modulus of binary mixtures were calculated from the experimental data. The calculated loss factors were dependent upon the mixing fraction, but almost independent of compressive stress and packing conditions. In order to describe the properties of binary mixtures, a simple two-phase model has been developed and compared with experimental data. Reasonable agreement between the model and the experimental data was obtained.