The transmission spectrum regarding the vertical incidence of a linearly polarized plane wave on the circular hole array on a submicron metal film is investigated. The maximum transmittance after the optimization of structural parameters is up to 0.896, which is much higher than the hole-filling ratio of the circular hole array, breaking through the expectation of traditional theories. After the analysis of the electric field distribution, waveguide mode, phase characteristics and dispersion relationship of the circular hole array on the metal film, the extraordinary transmission mechanism based on the circular hole waveguide on the metal film is investigated. A two-dimensional (2D) periodic optical lattice is formed above the circular hole array on the metal film due to the surface Bloch wave, and the electric field distribution center of the optical lattice is just above the circular hole part of the metal film. When the electric field mode of the optical lattice matches the transverse intrinsic electric field mode in the circular hole, the coupling efficiency will be large. If the phase matching condition is satisfied when the electric field mode propagates along the circular hole, the light in the circular hole can be effectively coupled from the circular hole, which thus generates a large transmittance. This mechanism can not only explain the extraordinary transmission phenomenon of a thick 2D circular hole array on a metal film but also be applicable to terahertz bands. If the circular holes are filled with a medium having a large refractive index, a large transmittance can be achieved when the wavelength is much larger than the hole radius.