A simply supported symmetric cross-ply laminated piezoelectric rectangular beam which is simultaneously forced by the transverse, axial excitations an d the excitation loaded by piezoelectric layers is considered. The model of which is a two-degree-of -freedom nonlinear system under the combination of the parametric and external excitations. Attention is paid to the averaged equation which is obtained in the case of 1:9 internal resonance. First, the bifurcations and chaotic dynamics by varying the coefficient of stiffness are found by simulation . Then the critical periodic solution which is undergoing the bifurcation scenarios is analyzed by Poincaré map. The Floquet multipliers verify the numerical prediction and show that the former bifurcation scenario is Neimark -Sacker bifurcation.