Abstract: Due to the low power conversion efficiency of parametric array, a method proposed in this paper can be used to improve the power conversion efficiencies of parametric arrays by adjusting the specific acoustic impedance. The Kuznetsov equation that describes parametric arrays is first studied, and the influence of Lagrangian densities on difference-frequency waves is analyzed. And the relationship between the Lagrangian density and the acoustic impedance is obtained. Subsequently, the method of arranging perforated plates around the parametric array to adjust the acoustic impedance is proposed. The proposed method is validated through numerical simulations. The results show that this method can improve the power conversion efficiency of the parametric array by using perforated plates to change the acoustic impedance.