The sound power sensitivity of viscoelastic damping plates is analyzed by using acoustic radiation modes. Two cases of plates, one with damping layer and the other with viscoelastic beams, are considered and compared. The influence of the thickness of the damping layer on the sound power sensitivity is found. The numerical examples show that it is effective for control of the sound power of plates by increasing suitably the thickness of the damping layer and locating reasonably the viscoelastic beams.