Abstract: Based on the distributed plasticity approach,a new kind of beam element,3-D materially nonlinear beam element with meshed sections,was presented to analyze the materially nonlinear behaviour of frame structures accurately,and a numerical example for the elasto-plastic analysis of a cantilever beam was given to illustrate the accuracy and efficiency of this approach.With this approach,beam sections are discretized into planar isoparametric elements at the integral points along the longitudinal direction of beam element,the stiffness matrices and resistant forces of sections are calculated by introducing the nonlinear stress-strain relations of materials and respectively integrating the stress-strain relations and stresses of sections,and the element stiffness and nodal resistant forces can also be evaluated with displacement interpolation functions when materials are in a nonlinear state.