A new integrated optimal design method is proposed for earthquake-resistant structures. Multi-objective genetic algorithm and response spectrum analysis are integrated to establish a general framework for multi-objective optimal seismic design of regular reinforced concrete single-column circular bridge piers. The optimization adopts structural sizing variables such as radius of circular section, longitudinal and transverse reinforcement steel ratios as design variables. And the optimal objectives include the initial material cost, the ratio between strength demand and capacity and the ratio between ductility demand and capacity. Through formulating the ductile seismic design problem as a multi-objective optimization problem, designers are able to keep prominent balance in some very important aspects of seismic design and deal with multi-objectives in a controlled manner to find the optimum parameters in a Pareto optimal sense.