To investigate the nondimensionalized ultimate strength and ductility behavior of stiffened steel pipe-section bridge piers subjected to a constant vertical load and cyclic lateral loads, the modified two-surface constitutive model and its finite element modeling were verified by comparing with the test results, and the effects of radius-thickness ratio, pier's slenderness ratio, stiffener's slenderness ratio and axial load ratio of the piers with eight stiffeners were investigated on the nondimensionalized ultimate strength and ductility.Some formulas based on the parametric analytical results were proposed to predict the nondimensionalized ultimate strength and ductility of piers.Numerical simulation results show that the nondimensionalized ultimate strength and ductility behaviors of the steel bridge piers could be notably improved when decreasing of radius-thickness ratio, pier's slenderness ratio, stiffener's slenderness ratio and axial load ratio.