A new method for system fragility is proposed in this paper with consideration of the seismic correlation of bridge fragments (piers, bearings, abutments). Firstly, 56 structure earthquake sample pairs are obtained by uniform design, which are used to get the seismic responses of components. Secondly, the joint probabilistic seismic demand model (JPSDM) is established by Matlab. Then the corresponding capability for each component are calculated. Finally, the bridge structure system fragility curve can be obtained with Monte Carlo Sampling (MCS). The nonlinear Opensees model of a three span continuous girder bridge is established as a case study. The results prove that larger errors will be brought in if the component correlation in fragility analysis is not considered.