Abstract: Considering the fact that the optimal design of an aseismicsteel frame is a multiobjective optimization problem, an optimization methodfor the multiobjective optimization design of aseismic steel frames based ongenetic algorithm (GA) was explored. A new ranking approach without usingpenalty function methods was presented to handle a constrainedmultiobjective optimization problem. This approach can deal with objectiveand constraint functions respectively. Based on the new ranking approach, aGA-based optimization method for constrained multiobjective optimizationproblems (CMOPGA) was advanced, and its flow chart was given. To minimizethe weight of an aseismic steel frame and its total dynamic strain energy, amathematical formulation of the multiobjective optimization design of anaseismic steel frame was established based on some corresponding codes. Anexample of two-bay six-story aseismic steel frame was provided, and acompromise principle of relative minimum distance was proposed for designersto select the compromise solution from a Pareto optimal set in the absenceof engineering experience. The optimal results show that it is effective forthe multiobjective optimization design of aseismic steel frames by usingCMOPGA.