The author presents one simplified technique and methodology for structural parameter identification and global damage detection from limited number of strong motion records. The time-invariant and time-varying parameters of structure are identified by using the off-line system identification method ARX and the on-line system identification method RARX respectively. The presence of damage is detected primarily by checking the changes of parameters during the earthquakes. Then, one procedure is introduced to convert MDOF structural system to equivalent SDOF system. The integral damage level of the equivalent SDOF system is detected by using the ductility factor and damage index. The damage index of the equivalent SDOF system can be considered as the integral damage level indicator of the MDOF system. The method is applied to