It is an important task for the government to ensure the earthquake-resistance capacity of a transportation network as a component of lifeline systems. In the recent 20 years great progress has been made to reduce the earthquake disaster in China. Especially the central government of China proposed to establish the prediction system, protection system and emergency salvage system against earthquakes, which is the macro policy to reduce the earthquake disaster. To help the government make decision with rational foundations, advanced technology is needed to be developed. With the above background, the seismic safety assessment system is developed in this paper.The aim of the seismic safety assessment system developed in this paper is to presents an effective tool for the seismic management of bridges over a large area, e.g., for a province. What has been done in this paper is as follows:(1) With the cooperation of technology of bridge engineering and information technology, a general design of the seismic safety assessment of bridges (SSAB) is accomplished. The basic database deals with the information from the design phase of bridges, from the construction phase, and the running phase. The information for earthquakes and seismic ground motion is also included in the basic database. The information needed for FEM (Finite element Methods) analysis is designed into the basic database. The information about FEM is related to the basic information of bridges, and can be renewed automatically with the change of information of bridges due to the maintenance of the bridges.(2) Various calculating and assessment methods are cooperated into the system, including seismic response analysis methods of bridges, assessment methods for seismic damages of bridges, the assessment methods for economic loss due to earthquakes, etc.(3) Establishing new random and response methods to evaluate the seismic responses of bridges with generally damping under uniform seismic actions. The approximately analytical modal combination coefficients (totally three of them, for modal displacement, modal velocity and between modal displacement and modal velocity) are presented to modify the computation efficiency. Numerical results from various example structures show that modal velocity and coupling terms between the modal displacement and modal velocity can be