To improve the precision and efficiency of nonlinear analysis, a three-node beam element based on isoparametric formulations is introduced. The stiffness matrices considering geometric non-linearity and distribution of Gauss points are given. By using this kind of beam element, the finite element program is developed which considers the effects of large rotations, large displacements and shear deformations. The material non-linearity is also considered by using von-Mises yield criterion and Zeigler kinetic hardening law. The program is proved to be feasible and efficient by comparing results with experimental data and those calculated using current commercial software. In addition, the dimensions of cross sections at two ends of the beam element can be different, so that the element can also be used to analyze tapered frames.