Abstract: Seismic fragility analysis is an important part of Performance-Based Earthquake Engineering (PBEE) proposed by Pacific Earthquake Engineering Research Center (PEER). Currently, most seismic fragility methods do not take the randomness of a structure into consideration, nor the dependence of structure random variables. Therefore, UD method is adopted to deal with the randomness of a structure and the dependence of structure random variables is considered through Nataf transformation. This comprehensive approach can consider not only the randomness of earthquake excitation and structural parameters, but also the dependence of structure random variables. A three span continuous girder bridge is analyzed as an example. The seismic fragility of the bridge is analyzed, considering the dependence of structure random variables. The analysis result indicates that this method can effectively take the dependence of structure random variables into account, neglecting the dependence may lead to the overestimation of bridge seismic fragility.