To further solve the problems of system stability and energy conversion efficiency in the development of wave energy utilization to deep water, the perforated damping plate is considered based on the existed point-absorber wave energy converter in this study. A new form of dual-buoy with supported column and perforated plate is proposed. Based upon the hypothesis of linear micro-amplitude wave theory, the influence of the perforated damping plates and the variation of configuration parameters on the hydrodynamic, motion and power conversion efficiency of the system are explored by means of the semi-analytical method of eigenfunction expansion and boundary matching and the multi-degree-of-freedom vibration theory. The results show that the opening radius of the damping plate will reduce the wave excitation force on the float. The float, the damping plate and the coupling radiation force will decrease with the increase of the opening radius of the damping plate. Its increase can also promote the relative motion of float and damping plate. The damping plate will make the system appear two coupling resonance frequencies. The optimal wave energy conversion efficiency at the smaller resonance frequency increases first and then decreases with the increase of the opening radius of the damping plate. The research results can provide a theoretical foundation for the engineering application of wave energy utilization in deep water and provide a basis for the optimization of oscillating-buoy wave energy converters.