Abstract: A method is derived to judge whether the calculation precision of the finite element model of bar element structures is senstive to the rotating stiffness of the joints so as to adjust its discrete method. based on the Zienkiewicz-Zhu error post-processing technique, a stress norm is defined to judge the calculation precision, and the equations beteween dispacements and forces are derived by considering the rotation stiffness of the joints. Taking the nodal displacements resulting from the trial calculations of the beam/truss element model as boundary condtions, this method gives the scopes of rotating stiffness suitable to be discreted by truss elements, beam elements, and beam-spring elements. A case study on an 32-leged structures is conducted to illustrate the feasibility and validity of the method in ANSYS.