Abstract: Based on the theories of Bernoulli-Euler beams and Vlasov’s thin-walled members, a new material nonlinear finite element model is developed by adding an interior node to the element and applying the independent interpolation to bending angles and warp. Factors such as shear deformation, coupling of flexure and torsion and warp induced by non-uniform torsion and second shear stress are all considered in this model. Material of the element is assumed to be perfectly plastic, complying with Von Mises’ yielding rule and the incremental relationship of Prandtle-Reuss. With the aid of the finite segment method, a certain amount of Guass points are distributed along the length of the element and in its cross section, thus the elastoplastic stiffness matrix being derived by numeric integration. Examples testify to the precision and validity of the model. It concludes that the model is applicable to the analysis of thin-walled structures.