A finite-element model for CFST members using a 3D composite beam fiber element is presented which accounts for the nonlinear constitutive models of steel and concrete separately. The model is proved to be valid by comparing the computational results of some test specimens with their experimental data. Using this model, a CFST arch bridge’s seismic response was calculated. The result indicated that the magnitude of displacements and moments at arch crown increases up to 10 percent caused by CFST hysteretic behavior which should be seriously considered during seismic design. Some measures and suggestions bring forward to guide the design and construction of this type of bridge.