Abstract: The problem of bifurcation and chaos in a thin rectangular plate under the electromagnetic fields and mechanic fields were studied. Base on nonlinear electro-magneto-elastic equations of thin rectangular plate under transverse electromagnetic fields and transverse loads, the vibration equations of two sides simply supported and two sides fixed thin rectangular plate were obtained The chaotic criterion of this system was obtained by Melnikov function method, and the vibration equation of the system was solved using numerical value method. And in the specific examples, the bifurcation diagram, the exponent Lyapunov diagram, the wave diagram of displacement, phase diagram and Poincare map were derived. The influences of magnetic parameter and mechanic loads on the vibration of the system were analyzed.