A　three-dimensional　linearized　elastodynamic　inversion　method　to　reconstruct　the　shape　of　scatterer　has　been　investigated.　The　surface　type　of　integral　representation　is　formulated　for　the　scattered　field.　Then　Kirchhoff　approximation　is　introduced　to　the　far-field　expression　of　scattering　amplitudes　in　the　integral　representation.　The　shape　reconstruction　of　the　scatterer　is　performed　by　the　inverse　Fourier　transform　of　the　approximated　scattering　amplitudes.　A　numerical　example　is　given　for　the　reconstruction　of　spherical　cavity　in　the　rod　by　the　Kirchhoff　inversion.