This paper introduces mechanics and electronic coupling mode of piezoelectric intelligent structures, and discusses the key technology and potential prospect of intelligent structures in application of vibration control. A multiple-input multiple-output transfer function model of piezoelectric plates is derived and an analogy for modal control between the piezoelectric structures and general ones is established. A concept, "piezoelectric vibration modes", is presented. Based on this concept and by experiment development, a "quasi-independent modal control" technique is presented, attempting to approach, with hardware as simple as possible, independent modal control. The experiment progress and results for multiple modal damping control show its effectiveness and practicality. The modal damping of piezoelectric intelligent structures can be increased enormously. They have good advantage and potential prospect in application of structure vibration control.