We developed a damage assessment package to assess buildings with various isolation systems. The package provides seven items to be used for damage assessment based on ARX method, MOESP method and double integration of acceleration data. The necessary condition for the package is to have a monitoring system with accelerometers at least at three levels i.e. on foundation, isolation layer and on top floor or roof of the building. Using this package, the performance of the isolation systems as well as superstructure during the earthquake can be quantitatively estimated. The package was tested for a 7-story base-isolated building in Yokohama, Japan. The building experienced the 2011 Tohoku Earthquake of the moment magnitude 9.0.