Abstract: In view of deformation theory and Mises criterion, we use the fictitious loads formulation to obtain the elastoplastic bending equations of Reissner's plates and Kirchhoff's plates, respectively, and solve them by the spline integral equation method just as the elasto-pro-blems. The equivalence of these two plate-models under polygonal simply-supported condition and axisymmetric bending is also studied here. The satisfactory results can be obtained even with a few of degrees of freedom.