Abstract: Analytical seismic vulnerability model of typically simply supported girder bridge was developed using the probabilistic seismic demand analysis approach. Based on collected data of damaged bridges from the 2008 Wenchuan Earthquake, a set of finite element model samples of bridges were produced by considering uncertainties with bridge parameters. Nonlinear dynamic transient analysis was preformed using the Wenchuan Earthquake ground motions, in which seismic peak responses of bridge components were recorded. By using the regression analysis method, a relationship between the ground motion intensity and components seismic demand is established. Once the limit states of bridge components at each bridge damage state were determined, seismic fragility curves were generated based on the logarithmic normal distribution assumption. Finally, by adopting the reliability theory and calculation, the lower and upper bounds of bridge system vulnerability were obtained. The generated seismic fragility curves can be used for seismic risk assessment and bridge retrofit prioritization.