Research conclusions: (1)For nonlinear elastoplastic seismic response analysis of the portal pier, which is a kind of time-varying structure of axial force, adopting the fiber plastic hinge model is feasible; (2)The calculation results show that, in accordance with the provisions regulating the stirrup case, portal pier potential plastic hinge region in varying degrees enters the plastic state, in 7(0.1g) and 8(0.2g) level, the average value of ductility ratio were 1.60 and 3.02, in 9(0.4g) level, the reinforcement ratio increase to 1%, the average value of the ductility ratio was 4.51 can meet the requirements of specification; (3)For the nonlinear time history response analysis, designers not only need to care about the ductility ratio whether meet the requirements of specification, but also need to pay attention to the state of the plastic hinge region section, to ensure that the structure does not collapse; (4) The theory and software of nonlinear time-history analysis is more and more mature, the various parameters needed for analysis should be clearly defined in the specification, which is convenient for technical staff to carry out accurate application; (5)Research results can be used for seismic design of railway bridge.