Abstract: Based on ANSYS finite element software, the performance of connections and the nonlinearities of geometry and material are considered, and the nonlinear finite element analysis of a steel frame with semi-rigid connections of top and seat angles with double web angles is conducted. The natural period of vibration, shear forces, displacements, accelerations of floors as well as the hysteresis loops of the steel-frame semi-rigid connection are obtained. The numerical results are compared with pseudo-dynamic experimental results, they are consistent well each other. The influence of semi-rigid connection’s flexibility on the steel frame is also explored, which provides some references for the design of a steel frame with semi-rigid connections and the amendment of the specification of the Steel structure in the future.