In general, characteristics of wind force for high-rise building dominantly depend on wake structure of the building and non-dimensional parameter of fluid dynamics such as Strouhal number. In urban area, many high-rise buildings exist sparsely, and peculiar patterns of unsteady turbulent flow fields around building cluster are caused by interaction between wake structures of buildings. Recently, many previous studies try to extract dominant turbulent structure around simple bluff body by constructing reduced order model (ROM) using proper orthogonal decomposition (POD). This study applies POD technique directly to the data on turbulent flows among the building cluster, and dominant turbulent structure which affects fluctuation of wind force is clarified. First, computation in the larger domain including multiple high-rise buildings is carried out by hierarchical Cartesian grid code named CUBE[1][2] developed by RIKEN R-CCS. In the calculation domain, circular-like region with a diameter of 2.4km is reproduced and time-spatio data of velocity and pressure are extracted from this computation. Then, validity of POD method for the complicated shape is examined by comparing the resulting cases based on the different analytical conditions on POD. Mainly the effects of data sampling frequency and extracting region on the POD modes are discussed. Finally, in order to clarify the effects of wake structure of windward buildngs on the wind force on a high-rise building, the obtanied POD modes and ROM are analyzed. POD modes which determine fluctuating characteristics of wind force for target building and windward buildings are identified, and wind force on target building are reconstrcted by ROM based on the selected POD modes. Then, the effect of wake structure of windward buildngs on the distribution for power spectrum density on wind force is clarified by analysis for the characteristics of time coefficient of POD modes.