A "smart" structure has many functions, including monitoring, repairing, shape formation, and learning. Recently, interest in applying a monitoring system to a structure for quality assurance and for evaluating seismic risk has been strong. Monitoring system is useful to diagnose the structural condition and detect structural damage and degradation. In this study, we developed a monitoring system to assess the structural integrity of a structure. This system includes a diagnostic system for structural damage and degradation based on mode parameters and wave propagation. The damage detection strategy is to first detect the damage sites globally by using an improved MDLAC (Multiple Damage Location Assurance Criterion) method, and then to evaluate the damage sites locally by using wave propagation. As a result, it is pointed out that there is a possibility to confirm the diagnostic system by utilizing these two methods.