The paper presents the method of the refined second-order plastic hinge analysis for planar steel frames subjected to dynamic loads. The material model used is the generalized Clough model in consideration of effects of axial and shear force on plastic limit state of cross-sections. Geometric nonlinearities of member and frame are taken into account by the use of stability functions in framed stiffness matrix formulation. Non-linear motional equation of structures was established by finite element method and solved by Newmark method combined with the modified Newton-Raphson method. Based on the obtained algorithms, the author has programmed a computational program and calculated the planar steel frames. From the calculated results, discussions and conclusions are presented.