(PU/UP IPNs)-BaTiO3 nanocomposites with different amounts of BaTiO3 nanopowder are prepared and polarized. The ferroelectric and dielectric properties are detected and the relationship between electric properties and damping properties are discussed in detail. Results indicate that the synergistic effects can be created successfully by elastic damping of polymer, frictional damping of BaTiO3, and piezoelectric damping of nanocomposites after poling. The nanocomposites increase the damping property evidently and sustain mostly ferroelectric and dielectric characters of inorganic phase. The introduction of BaTiO3 into IPNs decreases the resistivity, and this has advantages to enlarge the damping loss factor (tanδ).