Piezoelectric materials can be used for structural damping because of their ability to efficiently transform mechanical energy to electrical energy and vice versa. The electrical energy may be dissipated through a connected load resistance. In this paper, a new optimization technique for the optimal piezoelectric shunt damping system is investigated in order to search for the optimal shunt electrical components of the shunt damping circuit connected to the piezoelectric patch on a vibrating structure for the structural vibration suppression of several modes. The vibration suppression optimization technique is based on the idea of using the piezoelectric shunt damping system, the integrated p-version finite element method (p-version FEM), and the particle swarm optimization algorithm (PSOA). The optimal shunt electrical components for the piezoelectric shunt damping system are then determined by wholly minimizing the objective function, which is defined as the sum of the average vibration velocity over a frequency range of interest. Moreover, the optimization technique is performed by also taking into account the inherent mechanical damping of the controlled structure with the piezoelectric patch. To numerically evaluate the multiple-mode damping capability by the optimal shunting damper, an integrated p-version FEM for the beam with the shunt damping system is modeled and developed by MATLAB. Finally, the structural damping performance of the optimal shunt damping system is demonstrated numerically and experimentally with respect to the beam. The simulated result shows a good agreement with that of the experimental result.