Abstract: A computer method is proposed to determine the reliability of bridge when impacted by a sailing ship in this paper. The local damage distribution in the bridge structure caused by the ship impact is calculated by nonlinear FEM analysis. The local damage is represented by the density of material damage in the local area. The material damage, which is a function of the plastic strain and the plastic strain rate, is included in the bridge material model. The calculated local damage data, test data and the historical damage data of the bridge are analyzed by knowledge-based expert system to give the global damage index of the bridge structure. The global damage index is used to stand for the current safety status of the bridge. If the global damage index is higher than a given critical value, safety control on the bridge is advised to take or the bridge is simply discarded. Otherwise, the damaged bridge could continue to be in service, and its future safety level is predicted by assuming that some possible disasters such as being impacted by sailing ships, earthquake, etc are encountered in future. If the predicted future safety level is low, the damaged bridge should be repaired in advance. Finally, the Qing Jiang Gao Ba bridge was analyzed as an example to show the effectiveness of the method.