Stable localized hexagonal structure is obtained in Ar dielectric barrier discharge. Its spatiotemporal dynamics is measured. It is found that the discharge moment of the middle filament always precedes that of others. The interval between two adjacent discharges of one micro-discharge varies between a long interval an d a short one alternatively. The experimental results are analyzed and explained by a discharge model of wall charges. It is shown that the filament is affected not only by its own field but also by other filaments during the discharge.