In this paper, we established a bridge three-dimensional finite element model for the structural dynamic analysis according to the geometry and material properties of a bridge Li Gong Yi Qiao at Wuhan University of Technology. On the other hand, we tested the dynamic characteristics of the bridge under environmental excitation by means of bridge sensors arranged at different points. The modal parameters of the bridge were identified through fitting the admittance circle. The comparison between the measured results and the theoretical studies has shown that the low-order vibration frequency and mode obtained from finite element analysis generally consistent with those from test. The finite element model provides a scientific basis for condition monitoring of the bridge in actual operations.