Abstract: For the significant differences in structural weight and stiffness between a steel-concrete composite bridge and a concrete bridge, a four-span continuous bridge was taken as an example, a simplified SDOF model was built and the seismic demands were calculated with response spectrum method. The effects of the factors on seismic response of the bridge such as the weight of a superstructure, the stiffness of a column section, etc. are investigated through a parametric study. The aseismic potential and performance for a composite bridge are investigated by the comparison of seismic responses among a concrete bridge with solid columns, a composite bridge with solid columns and a composite bridge with hollow columns. It is shown that composite bridges have lower seismic demands than concrete bridges; composite bridges have superior aseismic potential and performance.