The controllability and stability of a smart plate with piezoelectric sensor and actuator laminae are analyzed from the viewpoint of energy. In terms of the power flow, the relation between the change of energy of the plate and the control voltage is derived. On the basis of power flow, some properties about the stability of the controlled plate are given. Moreover, some uncontrollable cases of the smart plate attached with a whole piezoelectric lamina actuator with spatially uniform distributed voltage are examined. Finally the effect of segmentation of the piezoelectric lamina on improving the controllability of the smart plate is discussed. The controllability and stability of a smart plate with piezoelectric sensor and actuator laminae are analyzed from the viewpoint of energy. In terms of the power flow, the relation between the change of energy of the plate and the control voltage is derived. power flow, some properties about the stability of the controlled plate are given. Moreover, some uncontrollable cases of the smart plate attached with a whole piezoelectric lamina actuator with spatially uniform distributed voltage are examined. Finally the effect of segmentation of the piezoelectric lamina on improving the controllability of the smart plate is discussed.