Abstract: To further study the seismic performance of steel frame systems, this paper proposes a variable cross-section-based steel frame system with semi-rigid connections, which is based on the forces acting on struts and beam-column-joint connections in steel structural engineering. First, the hysteretic behavior of the variable cross-section brace was examined by a seudo-static test. Second, the loadings of the pseudostatic test were compared with the results of ANSYS finite element analysis. Finally, the seismic performance of the system was investigated by times-history finite element simulation.Resultsshow that the seismic performance of the variable cross-section-based steel frame with semi-rigid connections is fine.