Abstarct: Structural health monitoring examines and evaluates the performance of the structure during its useful life. Structural response to dynamic loads, calculation of structural dynamic characteristics and detection of potential damage are among the goals of structural health monitoring. Monitoring of health of a structure and detection of damages are important to assess and extend the life time of the structure. Damage refers to all factors that cause adverse effects in useful operation of structure. In this thesis, the meaning of damage is assumed to be reduction of stiffness and mass of the structure. The damage detection methods in the structures are in order to find the location and intensity of damages; therefore, identification of damage is the first step for the structural health control systems. In this research, the aim is to model the structure with consideration of the damage, which leads to reduction of stiffness, and then by using topology optimization, location and intensity of damage will be identified. In the optimization problem, various objective functions have been studied. Minimizing the difference between structural natural frequencies and mode shape functions of the main structure and the model, has been considered for this purpose. Desgin variables of the problem are defined by using the well-known artificial material model in topology optimization context, called, Solid Isotropic Material with Penalization (SIMP). The finite element method is used to analyze and calculate the required parameters. In order to solve the optimization problem, the steepest descent method has been used and the sensitivity analysis is achieved. Finally, several numerical examples are presented for verification and effectiveness of the proposed method.