This letter proposes a method for rapid analysis of the scattering characteristics of large-scale arrays based on the regional decomposition strategy. To achieve array analysis, traditional infinitesimal dipole model methods use equivalent elements to characterize the mutual coupling effects between array elements. However, when the array is large, solving the mutual coupling matrix is often limited by hardware resources. This method utilizes the elements' electromagnetic periodicity and the diffracted waves' matching conditions, and derives the maximum subarray size based on the Floquet periodicity theorem. Treating the subarray as a new array element and reconstructing the mutual coupling matrix enable rapid array analysis within limited computing resources and are more suitable for scattering analysis of large-scale arrays. Numerical examples and comparisons with the literature verify the effectiveness and correctness of the proposed method.