Abstract: To find out the reason resulting in the crush of the girder of Zhaobaoshan Bridge in Ningbo during the construction, the approach of event tree analysis, which systematically takes into account any information on the uncertainties involved in the accident of structures, is applied to analyze the accident of Zhaobaoshan Bridge and is used to establish the accident scenarios qualitatively. The accident scenarios are calculated by simulation quantitatively, and the reason of the accident is inversed. The analysis reveals that there are three causes that are responsible for the accident of Zhaobaoshan Bridge: the overlarge force of some cables, the thinner of soleplate’s thickness and the influence of fluctuating wind on the girder. Also, it indicates that the approach of event tree analysis makes the accident analysis more systematical and comprehensive.