Abstract: Numerical simulation experiments on optical field distribution of one-dimensional metallic gratings with dielectric substances and sub-wavelength slits which are different in structure and parameter under transverse electric (TE) polarization excitation were carried out by using the method of finite-difference time domain. Physical mechanism was analyzed based on the theory of charge distribution on metal surface and the surface wave theory. The analysis showed that cylindrical surface waves were generated in metal slits and such kind of surface waves could break the diffraction limit to cause extraordinary transmission. The dynamic response of the dielectric cladding thickness to the transmission peak position and the dynamic relationship between the transmissivity and the wavelength when varying the thickness of metallic thin film were found by analyzing the surface charge distribution and excitation mechanism of Ag, thus the cylindrical surface wave was confirmed as one of the important factors that may cause extraordinary transmission. The theoretical analysis is consistent with the si-mulation results, which provides a good theoretical basis for an further study on the mechanism of extraordinary transmission and the selection of structural parameters under TE polarization excitation.