In spite of being a compact directional sound device, the parametric array loudspeaker (PAL) has often been criticized for its severe nonlinear distortion. In some preliminary studies, the nonlinear distortion is able to be reduced by using the linearization system based on Volterra filter identification, which models the nonlinear sound process of the PAL. However, the nonlinearity of the PAL changes with the input amplitude. When the input amplitude is high enough, there is strong high-order nonlinearity and the 2nd-order Volterra kernel cannot be accurately identified. Therefore, an improved identification method of the 2nd-order Volterra kernel is proposed to exclude the interference from the 4th-order nonlinearity.