Abstract: To investigate corrosion effects on the seismic fragility, a simplified single-pier was analyzed, and the corrosion damage model was built through the modification of materials' stress-strain relationship.Considering the randomness of input ground motions and the influence of site-type, the relationship between the seismic demand parameters and the ground motion intensity indicators was obtained by nonlinear dynamic time history analysis. After four damage indicators about bridge column are defined, the seismic fragility curves of bridges in different corrosion levels were presented.Resultsshow that bridges' seismic fragilities increase with the corrosion levels; this increasement is insignificant in the range of corrosion rate 10% ~ 15%.