Abstract: Vibrational power flow on combined plates with a change in mass and stiffness or with viscoelastic damping layer used widely in engineering is studied. The expressions of fie-cural displacement and other physical quantities are obtained using Laplace transformation and transfer matrix approach, then influences of changes in mass and stiffness of discontinuous material and the free damping layer on input power flow and transmitted power flow are discussed. The conclusinons provide theory basis for structural optimization design and reducing noise and vibration.