Abstarct: Civil infrastructures are very important for every society and include buildings, bridges, power plants, petroleum installations, geotechnical structures, etc. These civil engineering structures usually have complicated design, and are influenced by the excessive using, aging and so on. Due to these interactions, their ability to resist natural and unnatural events will decrease. Maintaining safety, reliability and using ability of these structures is essential. Therefore, it is important to monitor the change of structural state to identify probable damage locations and their measure. The Structural Health Monitoring (SHM) knowledge provides an approach for evaluation of safety and durability of structures during their life. One of these important infrastructures are bridges. Because of economic consequences, these structures are used despite of aging. So the ability for monitoring health of these structures is important. Structural health monitoring provides an efficient way to ensure the safety of a structure. Nevertheless, with the restriction of limited financial resources, only a small number of sensors could be available in structural health monitoring system (SHMS). Sensor system is a basic portion of SHMS. Unfortunately, the number of sensors installed in a structure is strongly limited by the corresponding costs. So, how to arrange the limited sensors in a structure is very important in the design and construction of an efficient SHMS. The main goal of this thesis is identification the location of sensors for structural health monitoring system for railway bridge. Due to moving train on the bridge the mode shapes of bridge change. Sensor placement of such structure cannot be performed by ordinary optimal sensor placement (OSP) techniques. Several approaches for finding optimal placement of sensors have been proposed in this thesis. One of them shows better results than ordinary OSPs.