In this study, a method is proposed for damage identification of 2D moment resisting frames by utilizing Craig-Bampton sub-structuring and GWO. Initially, an index based on the Discrete Wavelet Transform (DWT) of the first mode shape variation is employed to identify the potentially damaged substructures. Subsequently, the global structure is partitioned into damaged and undamaged substructures, making modal analysis of each substructure more computationally efficient, easier, and less time-consuming. Additionally, an iterative GWO procedure is conducted at a lower computational cost due to the reduction in the size of the decision variable vector, which corresponds to the number of elements in the damaged substructures. Finally, the extent of the damaged elements located in the suspected substructures from the previous stage is estimated based on the GWO results.