Abstarct: Structural health monitoring is one of the important fields in civil engineering for evaluation and long-term maintenance of structures. It is important to pay attention to small damages and timely prevention of damages, both economically and safely. One of the important methods of the health monitoring of structures is the dynamic method. Since the vibrational properties of a structure, including the frequency and modal shapes, are a function of its physical properties, so a change in the physical properties of a structure causes changes in its vibrational properties, so these changes can be considered as a sign Be considered as structural damage. Therefore, in this thesis, using the developed algorithm of Random decrement method, the properties of the structure and Modal shapes are obtained in order to be able to detect the failure of the structure by detecting changes in these vibrational properties. Random decrement method, in addition to eliminating noise, due to averaging, reduces the data needed for processing, which leads to a reduction in processing time. In this thesis, with three different tests, a three-storey building, a hinged beam and a four-storey building with real data, the proposed algorithm is validated and then with using the actual response data of a four-storey structure in Healthy and damage mode, the characteristics of the structure have been obtained and compared with the results of the article. Finally, it can be seen that the characteristics of the structure obtained from the algorithm in a short time and accurately equalizes the output of other methods.