<p>This study proposes a metallic nanostructure composed of double-symmetric triangular nanohole arrays and investigates the optical transmission characteristics of such structures with varying configurations. The finite element method (FEM) is employed to theoretically analyze the transmission properties of multiple structural designs. The excitation of surface plasmon polaritons (SPPs) on the metal surface, the coupling of localized surface plasmon resonance (LSPR) at the sharp vertices of the triangular holes, the plasmonic coupling between adjacent nanoholes, and the waveguide transmission modes collectively contribute to a unique dual-enhanced extraordinary optical transmission (EOT) phenomenon in the proposed double-symmetric nanohole arrays. By adjusting the geometric parameters of the triangular holes and the dielectric properties of the filling materials, the optical transmission characteristics can be effectively modulated. The findings provide valuable insights for applications in optoelectronic device design and biosensing.</p>