Abstract: In order to investigate damage localization, an experiment on an one-bay two-story spatial steel braced frame structural model was carried out. Four known damage patterns, including single, symmetric, asymmetric and multi-story damages, are simulated by removing corresponding braces. Modal parameters of undamaged and damaged structures are obtained utilizing the natural excitation technique (NExT) in conjunction with the eigensystem realization algorithm (ERA) from acceleration responses induced by hammer impacts and simulated ambient excitation. A method based on eigen-sensitivity analysis is employed to obtain the mass-normalized mode shapes. Furthermore, the damage index method and the damage locating vectors (DLVs) method are utilized respectively to identify the damage locations. It is demonstrated that the presented vibration-based methods are effective to damage localization.