In this paper, the model for thin rectangular plate coupled transverse invariable electromagnetic with uniform transverse forces was built.The boundary of this model was that four edges were simply supported. Based on this, the coupled vibration equations of thin rectangular plate were derived, and the heteroclinic orbit parameter equations of this thin plate vibration system were solved. Using Melnikov function method, the heteroclinic orbit's Melnikov function of vibration system were derived and solved. Finally, the chaos condition and judging criterion of this system about Smale commutation were given.Thus, we can study the bifurcation and chaos of thin rectangular plate coupled mechanical loads with electromagnetic. The method offered in this paper may be used to study the elasticmagnetic vibration of thin plate under different boundary conditions and different external loads.