Using full-vectorial, three dimensional, finite difference time domain (FDTD) simulator, greatly enhanced extraordinary optical transmission (EOT) is studied in a composite metal system, which is constructed by stacking a hexangular annular ring array over a hexangular hole array, perforated in a metallic film. In comparison with conventional periodic hole array, perforated in a single metal film, the composite metal system exhibits much stronger transmission amplitude and narrower band width. Such a novel behavior of EOT is well explained by the numerical results obtained from the distributions of electric field intensity, flowing maps of Poynting vectors and frequency dispersions. The results show that strongly excited surface plasmon polaritons (SPP) plays a dominant role in coupling light throughout the composite system.